Soil nitrogen(N)cycling enzyme activity serves as a crucial indicator for characterizing soil fertility and N transformation.To investigate the effects of long-term application of fertilizers on the soil enzyme activities correlated with N cycling in rhizosphere soil of double-cropping rice fields in southern China,our project was based on a continue 37-year fertilization localization field experiment,including four fertilization treatments:without fertilizer as a control(CK),single fertilizer(MF),rice straw residue and mineral fertilizer(RF),and 30% organic manure and 70% mineral fertilizer(OM).The activities of N cycling enzymes in the rhizosphere soil were measured,and their correlation with soil chemical properties was analyzed.The results were as follows:compared to MF and CK treatments,OM and RF treatments significantly increased the contents of total N(TN),organic carbon(SOC),ammonium N($\mathrm{NH}_{4}^{+}-\mathrm{N}$),nitrate N($\mathrm{NO}_{3}^{-}-\mathrm{N}$)and microbial biomass N(SMBN)in rhizosphere soil,and also increased rice yield.The urease(Ure)and nitrite reductase(NiR)activities of rhizosphere soil in OM and RF treatments were significantly higher than those in MF and CK treatments.The RF treatment significantly increased rhizosphere soil hydroxylamine reductase(HyR)activities compared to the other three treatments,by 21.7%,13.0%,and 8.7%,respectively.This finding shown that OM treatment significantly increased protease(Pro),nitrogenase(Nit),nitrate reductase(NR)and nitrous oxide reductase(Nos)in rhizosphere soil compared to RF,MF and CK treatments.In comparison to MF treatment,OM treatments increased Pro,Nit,NR and Nos activities in rhizosphere soil by 20.0%,26.1%,426.1% and 26.7%,respectively.Nonetheless,the activity of nitric oxide reductase(Nor)on rhizosphere soil was considerably higher in the CK treatment than in MF,RF and OM treatments.Pearson correlation analysis revealed a substantial positive correlation between soil NR,NiR,Nit,Nos,Ure,Pro and soil TN,SOC,$\mathrm{NH}_{4}^{+}-\mathrm{N}$,$\mathrm{NO}_{3}^{-}-\mathrm{N}$,SMBN as well as rice yield.Soil Nor activity was observed to have a significantly negative connection with soil TN,SOC,$\mathrm{NH}_{4}^{+}-\mathrm{N}$,$\mathrm{NO}_{3}^{-}-\mathrm{N}$,SMBN and rice yield.The findings presented above showed that soil chemical properties and yield were substantially related to rhizosphere soil N cycling enzyme activities.Redundancy analysis(RDA)showed that the first order axis could explain 93.34% of the enzyme activity in rhizosphere soil and soil $\mathrm{NO}_{3}^{-}-\mathrm{N}$,TN and SOC contents were the key factors affecting the pattern of rhizosphere soil enzyme activities.Therefore,the long-term application of organic materials such as organic manure and rice straw can enhance soil chemical and biological characteristics,stimulate soil N cycling enzyme activities,and effectively fertilize paddy soils by partially replacing chemical fertilizers.

The aim of this study was to investigate the effects of different nitrogen application levels and base-topdressing ratio on wheat leaf physiology,source-sink regulation of grain storage and yield in the middle and lower region of Yangtze River in Anhui Province.Using Baihumai 1 as the experimental material,three nitrogen application rates(180,210 and 240 kg/ha)with different nitrogen application levels and base ratios of 5∶1∶4,7∶1∶2 and 5∶4∶1 were set;through the determination of different source-sink indexes,in order to determine the appropriate wheat nitrogen fertilizer management model in the middle and lower region of the Yangtze River.The results indicated that with increasing nitrogen application rates(0 to 240 kg/ha),wheat leaf area index(LAI),post-flowering chlorophyll relative content(SPAD),and source organ biomass allocation showed an upward trend.The grain biomass allocation during maturity and the conversion rate of post-flowering source production capacity exhibited a trend of initially increasing and then decreasing,with the highest values observed at a nitrogen application rate of 210 kg/ha.At the same nitrogen application level,under the condition of a 7∶1∶2 base-to-topdressing ratio(base fertilizer∶tillering fertilizer∶jointing fertilizer),wheat plant had the highest leaf area index,while under a 5∶1∶4 ratio,chlorophyll content was highest.The grain biomass allocation during maturity and the economic coefficient were highest with the 7∶1∶2 base-to-topdressing ratio.Under the same base-to-topdressing ratio treatment,increasing nitrogen application improved the number of wheat spikelets and effective spikes,while the thousand-grain weight decreased with increasing nitrogen application.Grain yield showed an initial increase followed by a decrease with increasing nitrogen application,and at a nitrogen application rate of 210 kg/ha and a 7∶1∶2 base-to-topdressing ratio,wheat population potential storage capacity was large,grain-to-leaf ratio was high,and grain filling index was suitable.Wheat grain yield reached its maximum.Considering both high yield and efficiency,the optimum nitrogen fertilizer application rate of 210 kg/ha and the base-to-topdressing ratio of 7∶1∶2 were the best for the rice-stubble wheat Baihumai 1 in the middle and lower region of the Yangtze River in Anhui Province,allowing for maximum potential storage capacity and yield under these conditions.

Low temperature stress seriously affects the safe production of rice,especially machine-transplanted rice.In order to clarify the suitable plant growth regulator and spraying periods for machine-transplanted double-cropping rice,the early rice variety Zhongjiazao 17 and the late rice variety H you 518 were used as materials.The effects of different plant growth regulators(Uniconazole,C1;Abscisic acid,C2;Zhuanggubao,C3)and spraying periods(early rice:soak seeds,D1;one leaf and one core stage,D2;two leaves and one core stage,D3;before transplanting,D4;during the greening stage,D5;late rice:booting stage,F1;initial heading stage,F2;full heading stage,F3;one week after full heading,F4)on the yield and cold-resistant characteristics of machine-transplanted rice were studied.The results showed that among the three plant growth regulators,the Zhuanggubao treatment had the largest number of stems and tillers,the highest leaf area index,and the largest dry matter accumulation,which were significantly higher than the other two treatments.The yield of Zhuanggubao was the highest.The actual yield of early rice was 7.58% and 7.13% higher than that of uniconazole and abscisic acid treatments respectively.The actual yield of late rice was 13.54% and 11.59% higher than that of uniconazole and abscisic acid treatments respectively.In terms of spraying period,early rice was sprayed at the greening stage,and late rice was sprayed at the initial panicling stage,which had the best effect on improving various indicators of yield and the highest yield.Analyzing the components of yield,plant growth regulators and spraying periods mainly increased yield by increasing the number of grains per panicle of rice.The SOD,POD and CAT activities of early and late rice were highest in the grain-stuffing treatment.At the same time,spraying plant growth regulators during the greening stage of early rice and spraying plant growth regulators at the beginning of earing stage of late rice were more effective in increasing antioxidant enzyme activity.Taken together,the plant growth regulator for double-cropping machine-transplanted rice in Southern Hunan is Zhuanggubao,and spraying during the greening stage of early rice and spraying at the beginning of earing stage of late rice have the best cold-resistant and yield-increasing effects.

In order to explore the effects of different irrigation methods and nitrogen fertilizer management on late rice growth,development,yield formation,and nitrogen use efficiency,Y Liangyou 911 was used as test material.Two irrigation methods(W1.flooded irrigation;W2.moistening irrigation) and three nitrogen fertilizer managenments base,tiller,ear and grain fertilizer ratios(N1:5∶3∶2,N2:3∶4∶3 and N3:3∶4∶2∶1) were designed.No fertilization served as the control (CK1.flooded irrigation;CK2.moistening irrigation).Leaf area index,SPAD value of rice leaves,dry matter mass,yield formation and nitrogen use efficiency were determined under each treatment combination.The results showed that compared with W1,the LAI of rice treated with W2 was lower in the early growth stage and higher in the middle and late growth stages.The SPAD value of W1 treatment was higher,but there was no significant difference in SPAD value in the late growth period.Under the same irrigation conditions,compared with N1,N2 and N3 treatments it could delay the decline of LAI and SPAD values in the late growth period of rice.W2 treatment could significantly increase rice dry matter accumulation by 6.61%-16.37% compared with W1 treatment.Under nitrogen fertilizer treatment,the dry matter mass was higher in the early and middle stages of growth with N1,and the dry matter mass was higher in the later stages with N1 and N3.The yield increase of W2 mode was 7.59%-10.47% compared with W1 mode.The yield of W2N3 treatment was 3.24%-14.53% higher than that of other treatment.Although the effective panicle number was lower in W2N3 treatment,other yield components were increased,which resulted in higher yield.During the two years,W2N2 and W2N3 had higher values of total nitrogen accumulation and nitrogen absorption efficiency,W2N3 had higher values of nitrogen agronomic utilization,nitrogen partial productivity and nitrogen harvest index,and W1N3 had the higher value of physiological nitrogen utilization.In conclusion,irrigation methods and nitrogen management significantly affect rice yield and nitrogen uptake and utilization.The W2 (moistening irrigation) coupled with N3 (base fertilizer∶tillering fertilizer∶ear fertilizer∶grain fertilizer=3∶4∶2∶1) nitrogen management method is more conducive to rice dry matter accumulation,yield improvement and efficient use of nitrogen fertilizer,which can not only meet high yield,but also play a role in water saving.It is the best coupling method of water and fertilizer.

In order to investigate the effect of reducing nitrogen and increasing density on the yield formation characteristics of ratooning rice,hybrid rice variety Chuangliangyou 669 was used as the material to conduct two years of field experiments under conditions of three nitrogen application rates(N1:180 kg/ha;N2:153 kg/ha;N3:126 kg/ha)and two plant row spacing(M1:20.0 cm×16.7 cm;M2:16.7 cm×16.7 cm).The results showed that:reducing nitrogen reduced the leaf area index(LAI)of ratooning rice,but increasing density within a reasonable range of nitrogen reduction could increase the LAI of the main and ratooning seasons.The LAI of N1M2 and N2M2 was higher in the interaction treatments.Reducing nitrogen and increasing density both reduced the SPAD value of ratooning rice leaves,but the effect of density was not significant.Reducing nitrogen led to a decrease in dry matter weight,while increasing density could significantly increase dry matter weight.The interaction treatment of N1M2 and N2M2 had a higher dry matter weight.Reducing nitrogen reduced the yield of ratooning rice,but increasing density within a reasonable range of nitrogen reduction could increase yield.The interaction treatment of N1M2 and N2M2 had a higher yield.Reducing nitrogen significantly reduced the number of effective panicles in the main season,the total number of grains per panicle,and the regeneration rate and number of effective panicles in the ratooning season.However,increasing density had a compensatory effect on the number of panicles.Reasonable nitrogen reduction and density increase(N2M2)could coordinate the relationship among yield components and achieve higher yields.The correlation analysis showed that reasonable nitrogen reduction and density increase increased the effective number of panicles and total grains per panicle in the main season,as well as the effective number of panicles in ratooning season mainly by increasing LAI and dry matter weight of the main and ratooning season,and thereby improving the yield of ratooning rice.Overall,the nitrogen reduction and density increase treatment N2M2(nitrogen rate of 153 kg/ha,plant row spacing of 16.7 cm×16.7 cm)can save 15% nitrogen and achieve a higher yield.

To improve seedling blast resistance of rice cytoplasmic male sterile(CMS)line Taonong1A and its maintainer Taonong1B,the Chinese local rice variety Gumei 4 was used as the donor parent harboring the broad-spectrum and durable blast resistance gene Pigm,and the Pigm-tightly-linked codominant marker T9E3 was developed and employed in marker-assisted selection(MAS)breeding practice.T9E3 showed clear and stable polymorphism between the donor and acceptor parents,amplifying a 926 bp DNA band from Gumei 4 genome,while the PCR product from either genome of Taonong1B or Taonong1A was about 2 000 bp.Greenhouse inoculation assay was performed using thirty-two Magnaporthe oryzae isolates collected from different rice areas,Gumei 4 and the improved rice lines showed much higher resistance frequency(90.63%)than that of two acceptor parents Taonong1B and Taonong1A(9.38%).Accordingly,Gumei 4 and the improved rice lines showed high-level seedling blast resistance(0 grade)but highly susceptible(8 grade)for two acceptor parents in natural nursery.Three blast resistant CMS pure lines(Taonong1A-Pigm-1—Taonong1A-Pigm-3)and the corresponding resistant maintainers(Taonong1B-Pigm-1—Taonong1B-Pigm-3)were preliminarily bred through MAS breeding,and one pair of them,Taonong1A-Pigm-2/Taonong1B-Pigm-2,was screened for potential application duo to the high-level blast resistance and elite sterility,agronomic and yield traits.Taonong1A-Pigm-2 showed complete male sterility with nearly 60% typical abortive pollens and 40% round abortive pollens,higher stigma exsertion rate(71.1%)and lower enclosed spikelet rate(33.6%),Taonong1B-Pigm-2 exhibited excellent agronomic and yield trait indexes,such as moderate sowing-heading duration(69 days),plant height(76.2 cm),main panicle length(28.1 cm),panicles per plant(15.8),spikelets per panicle(115.3)and 1000-grain weight(27.7 g)。New parent materials were created for the application of cytoplasmic male sterile(CMS)line hybrid rice breeding,and the comprehensive improvement of seedling blast resistance and characters of Taonong1A and Taonong1B were realized.

Knockout mutants ossaur55-1 and ossaur55-2 obtained by CRISPR/Cas9 technology in Francis background were used as research objects to study whether they affect the changes of agronomic traits such as plant type,leaf color,ear weight per plant and seed setting rate of rice.To explore whether OsSAUR55 regulates rice plant type by participating in GA pathway,and to provide theoretical basis for regulating rice plant type by related hormone pathway.The main agronomic traits of wild type(WT)and knockout mutant in adult plant stage were examined,including plant height,ear length,ear weight per plant,ten grain length,ten grain width,blade length,and blade width.Chlorophyll content and net photosynthetic rate of wild type and mutant leaf were measured by chlorophyll meter and photosynthetic rate meter.Real-time Fluorescence Quantitative PCR(qPCR)was used to determine the expression of OsSAUR55 gene in different tissues and different time points of rice seed germination.The subcellular localization of OsSAUR55 protein was observed by prokaryotic expression method.The contents of endogenous hormones(GA and IAA)in wild type and mutant were determined by liquid chromatography-tandem mass spectrometry(LC-MS/MS).The expression of genes related to GA pathway was further analyzed.In the adult plant stage,mutant ossaur55-1 and ossaur55-2 showed significant phenotypic changes,in which the mutant was significantly shorter in plant height,greener in leaf color,increased in chlorophyll content,decreased in photosynthetic efficiency,decreased in seed setting rate,decreased in 1000-grain weight and decreased in panicle weight per plant than the wild type.The quantitative results showed that OsSAUR55 expression was the highest in the plumule,but not in the flag leaf.Confocal results showed that OsSAUR55 may be localized in cell membrane and nucleus.The results of hormone detection showed that the content of GA₄ was decreased significantly.Gene expression analysis showed that the expression levels of genes KAO,GA13ox1,GA20ox1 and KO1 in the GA synthesis pathway were significantly higher than those of the wild type,and the expression levels of GA2ox5,GA2ox8 and GA2ox9 in the GA metabolic pathway were also significantly higher than those of the wild type.It is preliminarily speculated that the deletion of OsSAUR55 gene led to the decrease of endogenous GA₄ content,which may regulate rice plant type through GA pathway,and then affect rice yield.

In order to investigate the reasons for the differences in plant height between SSSL-B50 and HJX74,an F₂ population was constructed by backcrossing SSSL-B50 with HJX74 for genetic analysis and gene mapping of the plant.The genetic analysis showed that F₁ plants exhibited tall plant height.And the separation ratio within F₂ was 3:1(χ²=0.18<3.84)between the tall plant individuals and the semi-dwarf ones,which indicated that the tall plant height of SSSL-B50 was a dominant trait.Based on the linkage analysis between the marker genotypes and phenotypes of plant height in the F₂ population,the gene controlling tall plant height was mapped between markers S18 and X161 within the 38.38—39.07 Mb interval of the substituted segment on chromosome 1.Moreover,it was found that the known gene of "Green revolution",SD1,fell to the mapping interval.Through amplification and sequence alignment of SD1 gene in Oryza glumaepatula,SSSL-B50,and HJX74,it showed that a 280 bp deletion in CDS in HJX74 compared with Oryza glumaepatula and SSSL-B50.The qRT-PCR results showed that the expression level of SD1 was significantly higher in the second,third,and fourth sections of SSSL-B50 stem than in HJX74.The comparison of the SD1 gene sequence of Oryza glumaepatula with the previous reported results showed that the base substitutions occurred at two sites (E100G, Q339R) in the encoded amino acid.The results revealed that the tall plant height of SSSL-B50 was controlled by SD1.Furthermore,a new allelic type of SD1, SD1^Glu,was identified in Oryza glumaepatula.

In order to determine the effect of allele variation in DEP1 locus on quality traits and metabolic profile of grains in rice,the high quality japonica cultivar Daohuaxiang and its erect panicle type mutant dep1-1 were used.The grain quality traits and differential metabolites between wild-type and mutant dep1-1 were measured.The results showed that the mutant dep1-1 had a single base A inserted into the fifth exon of the DEP1 gene,leading to premature termination of translation and the deletion of the cysteine-rich region in G-protein gamma subunit.Compared with wild-type cultivar,the grain length,appearance,viscosity,balance,taste value,peak value,recovery value and peak time of mutant dep1-1 were significantly decreased,while amylose content, acidity value and hardness were significantly increased.Compared with wild-type cultivar,37 metabolites were significantly up-regulated in dep1-1,while 45 were significantly down-regulated.KEGG analysis showed that these differential metabolites were mainly enriched in galactose metabolism,fatty acid biosynthesis,starch sucrose metabolism,linoleic acid metabolism,ABC transporters,and phenylpropanoid biosynthesis pathways.Compared with wild-type cultivar,the contents of sucrose,D-raffinose,raffinose,D-(+)-maltose D-(+),betaine and indole of grains significantly increased in dep1-1,while those of stearic acid,palmitic acid,L-leucine and indole-3-acetic acid significantly decreased.These differential metabolites preliminarily explained the physiological and biochemical mechanism of grain quality changes in dep1-1 mutant.

In order to understand the application effect of rice-straw application combined with decomposing agent on tobacco.The pot culture experiment was conducted to analyze the variation of the tobacco's growth,yield,chemical composition and coordination after the rice-straw application combined with chemical fertilizer and decaying agent containing different microbial dominant strains respectively,the research object was to explore the effects of rice-straw application combined with decomposing agent on the tobacco's growth,yield and quality.The results showed that the rice-straw application combined with decaying agent significantly increased the stem circumference,maximum leaf area,biomass,yields and the ratio of medium & superior grade of tobacco.The rice-straw application combined with decaying agent significantly lowered nicotine content of the upper tobacco,and increased its' total sugar content,reducing sugar content and total sugar-nicotine ratio,which resulted in reducing the irritability,bitterness and pungency of the upper tobacco and improving its' smoking quality;meanwhile,the rice-straw application combined with decaying agent significantly raised the content of total nitrogen,total sugar and reducing sugar in central tobacco,but there were no obvious variations for the ratio of total nitrogen to nicotine,reducing sugar total nitrogen and reducing sugar to nicotine,which meant the effect of rice-straw application combined with decaying agent on the central tobacco's chemical coordination was not significant;moreover,the rice-straw application combined with decaying agent increased the content of total sugar and reduced sugar in lower tobacco,and raised its' ratio of reducing sugar to total nitrogen and sugar to nicotine,which was beneficial to increase the aroma of lower tobacco and reduce its' impurity.According to the results of principal component regions between tobacco's agronomic characters and biomass,chemical composition and coordination indexes of different parts of cured tobacco,the rice-straw application combined with the decomposing agent containing dominant microorganism of bacteria+fungi or bacteria+fungi+actinomycetes had no significant difference in promoting tobacco's growth,yield and quality.Therefore,the rice-straw application combined with the decomposing agent containing different types of dominant microorganism could promote tobacco's growth,rationalize the chemical composition of upper and lower tobacco,and be beneficial to improve its sensory quality and increase tobacco's yield and quality.

To explore the effects of long-term multi-cropping patterns on soil structure and organic carbon distribution in paddy fields. With fallow-rice-rice (WF-R-R) model as the control, four multi-cropping models were set up: rape-rice-ric (RP-R-R), Chinese milk vetch-rice-rice (MV-R-R), Potato-rice-rice (PO-R-R), ryegrass-rice-rice (RG-R-R). The results showed that in 5—10 cm soil layer, the contents of water-stable aggregates with size of >2 mm were increased in the multi-cropping pattern. The RG-R-R mode was 11.26 percentage points higher than the control, and the mean weight diameter (MWD) was significantly higher than the control. In 0—5 cm soil layer, the organic carbon content was increased by multi-cropping mode. The SOC content in RG-R-R mode was the highest in 0—20 cm soil layer, and the SOC content in each soil layer was increased by 9.57% (0—5 cm), 4.45% (5—10 cm) and 5.96% (10—20 cm), respectively, compared with the control. With the deepening of soil layer and the decrease of aggregate particle size, the soil organic carbon content in the multi-cropping model increased more significantly than that in the control. When the size was <0.053 mm, the soil organic carbon content in the RG-R-R model was significantly higher than that in the control. The contribution rate of soil aggregate organic carbon mainly came from the >2 mm grain size (59.03%—79.33%). In the 5—10 cm soil layer, the contribution rate of aggregate carbon in the >2 mm size of MV-R-R, PO-R-R and RG-R-R models was significantly increased by 8.5, 7.18 and 14.65 percentage points compared with the control. In conclusion, in this study, the ryegrass-rice-rice (RG-R-R) model was conducive to soil aggregate stability and organic carbon fixation in southern paddy fields.

The physiological and biochemical indices of cold tolerance in common overwintering cultivated rice seedling were studied for providing theoretical basis for the innovation and utilization of overwintering cultivated rice germplasm. A total of 20 overwintering cultivated rice germplasms were selected as experimental materials,altogether five physiological and biochemical indices such as chlorophyll,malondialdehyde and SOD activity in rice seedling were measured and analyzed under both normal temperature(25 ℃)and 4 days of low temperature(4 ℃)stress. The five cold tolerance indices under normal temperature condition displayed extremely significant phenotypic differences among all tested materials from seven different provinces in China. The cold tolerance index such as chlorophyll and soluble sugar content apparently declined after chilling stress,but exhibited an inconsistent rate of decline among all experimental materials,ranged from -36.46% to -90.31%,-70.54% to -94.03%,respectively. While the cold tolerance indices such as malondialdehyde,proline and SOD activity in all tested rice seedlings displayed disparate response to cold chilling and exhibited an inconsistent rate of rising or falling. Among all tested materials,the malondialdehyde content in three tested materials such as Huangnuo 2,Wanjingnuo M99037 and Changnongjing 3 exhibited significantly decline after chilling stress,the remaining seventeen tested materials exhibited a significant rise. The proline content in eight tested materials such as Tiejingdao 4,Zhendao 7 and Jindao 1187 exhibited a significantly rising after being chilling stress,but the remaining twelve tested materials exhibited a significant decline malondialdehyde content value. The SOD activity in Ewandao 15 and Jinjingzasi exhibited an inconspicuous decline after chilling stress,while the SOD activity in the remaining eighteen tested materials exhibiteda significant rise. Only 2 pairs of extremely significant PCC values among the five cold tolerance indices were calculated under the normal temperature environment,while 8 pairs of extremely significant PCC values were calculated after chilling stress. Apparently,the number,strength and direction of correlations among the 5 cold tolerance indices were easily varied after chilling stress. On the whole,the cold tolerance indices in rice seedling under both normal temperature and low temperature exhibited significant difference owing to the different genetic background of overwintering cultivated rice.

In order to study the effect of low temperature on the ultrastructure of pollen grains and flag leaves of rice in cold regions,Japonica rice varieties Kongyu 131 and Longjing 25 with strong cold tolerance and varieties Longjing 11 and Longjing 28 with poor cold tolerance were selected as research materials in cold regions,low temperature treatment during flowering period (13,15,17 ℃),the samples were observed and photographed using scanning and transmission electron microscopy.The results showed that:Under low temperature stress,the reticular patterns on the pollen grains of Kongyu 131,Longjing 11 and Longjing 25 changed significantly,the reticular carvings on the surface of rice pollen grains changed from deep to shallow,with the decrease of stress temperature,the reticular carvings on the surface of rice pollen grains changed from deep to shallow,reduction of surface protrusions,the surface of pollen grains became smooth,which was not conducive to the attachment of pollen on stigma because made the surface of pollen grains smooth;however,the pollen grain surface characteristics of Longjing 28 under low temperature stress were not significantly different from those of the control.With the decrease of temperature,starch grains in chloroplasts of rice varieties decreased significantly,osmiophilic grains increased significantly,grana became loose,and the proportion of superposed thylakoid membranes decreased;however,under the influence of low temperature,the varieties Longjing 25 and Kongyu 131 with strong cold tolerance and the varieties Longjing 11 and Longjing 28 with poor cold tolerance did not show the same law in grana lamella and matrix lamella,while the changes in starch grain synthesis and osmiophilic particle number were consistent.Compared with rice pollen grains,the effect of low temperature on sword leaf ultrastructure was more obvious. Under low temperature stress,leaf function declined and chloroplast photosynthetic changed among rice varieties with strong and poor cold tolerance were significantly different,with obvious rules.

Agronomic characters,lodging,quality and yield of eight japonica(glutinous)rice varieties mainly planted in Anhui Province in recent years were analyzed under the two cultivation methods of cave sowing and transplanting,so as to clarify the main limiting factors of yield under the light and simplified planting conditions such as cave sowing,and provide reference for screening and breeding new rice varieties suitable for light and simplified planting.Field plot experiment was used. Field plot experiment was used, two cultivation methods were set up, namely hole sowing and transplanting, to investigate the seedling emergence rate in the field; lodging index for different varieties; to take five plants at the maturity stage, to investigate the plant height, the effective number of spikes per plant, the length of spike, the number of grains in the spike, the fruiting rate, the quality of 1 000 grains, and the yield of each material; and to determine the roughness, the rate of polished rice, the rate of whole polished rice, the length-to-width ratio, the content of straight-chain amylopectin, and gelatinized rice consistency according to the ministry standard after harvesting the paddy grain samples.The germination rate of the varieties was better under laboratory conditions,but the seedling emergence rate decreased significantly under cave sowing conditions.Wankennuo No.1,Dangjing No.8 and Jiahua No.1 had higher seedling emergence rates in field.Lodging index of all varieties under cave-sowing condition was lower than that under transplanting condition,among which Jiahua 1 and Lüxiangjing 28 had the strongest lodging resistance under cave-sowing condition.The seed setting rate and 1000-grain weight under hill-point sowing were higher than those under transplanting,but the yield per plant,grain number per panicle,effective panicle number per plant and panicle length were lower than those under transplanting.There was a significant positive correlation between yield per plant and number of solid grains per panicle under the cave-planting method,and a significant positive correlation between yield per plant and number of solid grains per panicle and seed setting rate under the transplanting method.The amylose content of rice under the acupoint direct seeding method was lower than that under the transplanting method,and the glue consistency and alkali loss value were higher than that under the transplanting method.The germination rate of cave sowing was significantly lower than that of laboratory sowing.Compared with the traditional seedling transplanting method,the lodging resistance of rice varieties under the cave-planting method was enhanced,but there was no significant difference in the lodging resistance of most varieties under the two methods.The yield per plant under the hole direct seeding method was lower than that under the transplanting method,and the main limiting factors were the number of grains per panicle and effective panicle per plant.The direct planting rice had better taste than transplanting rice in amylose,gum consistency and alkali loss.

In order to excavate the mycovirus resources in Ustilaginoidea virens and deeply analyze the relationship between the genome organization and function of a novel mycovirus,it took a U.virens strain Uv321 with abnormal phenotype,isolated from Hainan Province,as the research object,and identified the species of the novel mycovirus in the strain Uv321 on the basis of the previous meta-transcriptome data,a series of studies have been carried out around the novel mycovirus.The results showed that a novel mycovirus was identified in strain Uv321,named Ustilaginoidea viruses botourmiavirus 7 (UvBV7).The genome of UvBV7 is positive single-stranded RNA(+ssRNA),with a total length of 2 406 nt and a GC-content of 53.78%,containing an open reading frame(ORF)encoding RNA-dependent RNA polymerase(RdRP),which encodes 643 amino acids with a molecular weight of about 72.727 ku.The prediction of the protein secondary structure of the viral terminal showed that the 5' and 3' terminal bases of UvBV7 were complementary and paired,forming a hairpin structure.The BlastP alignment showed that UvBV7 had the highest similarity with the virus Erysiphe necator associated ourmia-like virus 72,which belonged to the genus Botoulivirus in the family Botourmiaviridae,but only 44.52%.The multiple alignment results based on the RdRP sequences of UvBV7 and other similar viruses showed that there were 8 conserved domains in the RdRP amino acid sequences of UvBV7 and the members of the family Botourmiaviridae.The GDD motif was found in the Ⅵ conserved domain,which is the typical highly conserved core motif of viral RdRP proteins.The phylogenetic tree constructed based on the amino acid sequence of the viral RdRP also indicated that UvBV7 clustered with the members belonging to the genus Botoulivirus.Therefore,UvBV7 is a novel mycovirus belonging to the genus Botoulivirus in the family Botourmiaviridae.The results of dual cultures of different strains of U.virens showed that UvBV7 could be transmitted horizontally between vegetative compatibility strains,but the mycelial tip-ribavirin,heat-ribavirin and protoplast regeneration-ribavirin treatments were unable to eliminate the mycovirus UvBV7 in strain Uv321.In conclusion,this study not only enriched the diversity of mycoviruses in U.virens,but also provided potential biocontrol agents with hypovirulence for the biocontrol of rice false smut.

The long-term field experiment on planting and turning over Chinese milk vetch was conducted to explore the effects of different incorporation amount of Chinese milk vetch on nutrient uptake,nutrient use efficiency,and yield of single cropping rice and to determine the optimal application rate of fresh Chinese milk vetch in south Henan rice area.There were eight treatments,CK(no fertilizers),CF(conventional fertilization),and six application levels(22.5,30.0,37.5,45.0,52.5 and 60.0 t/ha)of Chinese milk vetch.Experimental results showed that compared with CK,the conventional fertilization treatment and Chinese milk vetch treatments increased rice grain yields by 21.72% and 19.23%—29.20%(P<0.05),respectively.In all the treatments of application of Chinese milk vetch,the maximum N,P and K content and accumulation in rice grains were obtained under the treatment of Chinese milk vetch application at 52.5 t/ha,but when continuing to increase the application rate,the nutrient content and accumulation in rice grains were significantly reduced(P<0.05).The application of Chinese milk vetch at 37.5—60.0 t/ha significantly increased the above-ground nitrogen,phosphorus and potassium accumulation compared with CK.The application of Chinese milk vetch at 22.5—37.5 t/ha significantly improved the agronomic efficiency and partial factor productivity of P and K(P<0.05).Comprehensively,the long-term incorporation of Chinese milk vetch at 22.5—37.5 t/ha is conducive to the stable production of rice yield and the absorption of N,P and K,thereby improving the rice nutrient utilization efficiency of N,P and K in south Henan Province.

In order to explore the gene expression regulation mechanism in the formation of reactive oxygen species (ROS) induced by heat stress,heat stress treatments were set at seedling,heading and filling stage to investigate the dynamic change of ROS accumulation in rice,respectively.And the Quantitative Real-time PCR (qRT-PCR) was used to analyze the expression pattern of nine respiratory burst oxidase homologue (Rboh) encoding genes (OsRboh1-OsRboh9) in rice under different growth stages.Results showed that the ROS accumulation in rice leaves and grains significantly increased with the extension of heat stress.The ROS content increased slowly after 7 days of heat stress at seedling stage, while increased continuously after heat stress during the heading stage and early filling stage (1-10 d) in rice grains. Expression levels of the nine OsRboh family genes continuously increased with the extension of heat stress at seedling and heading stages,and OsRboh7 and OsRboh5 showed higher expression levels under heat stress.The expression levels of OsRboh1,OsRboh5 and OsRboh9 were continuously increased,while other genes showed a change tendency of increasing initially and then decreasing under heat stress at filling stage.The expression levels of OsRboh7 and OsRboh5 were all reached to a high level at seedling,heading and filling stage under heat stress.Furthermore,higher expression levels of OsRboh7 and OsRboh5 were showed in various tissues and organs of rice such as seedling leaves,flag leaf,floret,lemma,palea,stamen,pistil and grain.The higher induced range of gene expression levels in OsRboh7 and OsRboh5 by heat stress was shown in seedling leaves,floret,stamen,pistil and grain.Taken together,OsRboh7 and OsRboh5 were mostly remarkably responsive to heat stress at different growth stages among the OsRboh family genes in rice,which indicated that OsRboh7 and OsRboh5 played a vital role in the regulation of ROS formation pathway in rice under heat stress condition.

To explore the function and possible molecular mechanisms of amino acid transporters (AATs),firstly,a new hidden markov model was established to identify the members of the rice AAT family,and a phylogenetic tree was constructed to analyze the evolutionary relationship of AAT members between rice and Arabidopsis;secondly,the promoter,protein structure,and functional domain of rice polyamine transporter gene 1 (OsPUT1) were analyzed using bioinformatics methods;thirdly,the subcellular localization of OsPUT1 was determined by constructing the OsPUT1-GFP vector and expressing it in rice protoplasts;fourthly,the expression patterns of OsPUT1 gene in different tissues and under different stress conditions were detected using qRT-PCR;finally,the function of OsPUT1 gene was preliminarily studied using the OE,Nip and RNAi lines.The results showed that there were 96 OsAATs divided into 13 subfamilies in rice;the PUT subfamily contained 6 OsPUTs,among which OsPUT1 and AtPUT3 had the closest genetic distance and were distributed in the same branch.The promoter of OsPUT1 gene contained cis-acting elements related to growth and development,light regulation,plant hormones,and stress response;OsPUT1 protein contained the polyamine transporter domain PotE,and subcellular localization experiment indicated that it was located on the cell membrane;the expression of OsPUT1 gene was relatively high in leaves,while was low in flowers;gene expression was inhibited by JA,mannitol,and ABA,while decreased and then returned to normal under low temperature stress,yet increased and then decreased under SA,Spm and paraquat treatment,however,under sodium chloride treatment,the gene expression level first increased,reached its peak at 1 h,then decreased,reached its lowest at 12 h,and returned to normal levels at 24 h;OE lines significantly reduced resistance to paraquat,while RNAi lines significantly increased resistance to paraquat.Overall,the OsPUT1 protein might have the function of transporting PA and participating in stress response.

In order to promote the breeding of high quality grain shape Japonica rice varieties,a natural population consisting of 295 Japonica rice varieties collected from around the world was used as test material for phenotypic analysis of five grain shape-related traits,including grain length,grain width,grain thickness,aspect ratio and thousand grains weight,between 2018 and 2019,combined with 788,396 SNPs obtained by resequencing,and genome-wide association analysis using the MLM model of TASSEL 5.0.Haplotype analysis was performed on all the genes in the QTL intervals that were jointly detected during the two years and controlled multiple shape-related traits, and candidate genes for high quality rice grains were mined by combining the results of previous studies and functional annotation of the genes. The results showed that there was extensive phenotypic variation for the five grain shape-related traits,all of which were approximately normally distributed,and most of the grain shape-related traits were significantly or highly significantly correlated with each other. And a total of 221 QTLs significantly associated with rice grain shape-related traits were detected under the threshold condition of P≤5.46×10^-6,which were distributed on all 12 chromosomes of rice,and phenotypic contribution was 8.62%-20.73%, of which, seven QTLs were jointly detected in two years, and combined with the haplotype analysis and functional annotation of the genes, it was hypothesized that LOC_Os12g 44290 was a new candidate gene for rice grain shape. In summary,this study used genome-wide association analysis for QTL localization and candidate gene analysis for grain type-related traits in 295 Japonica rice varieties,providing a theoretical basis for breeding Japonica rice varieties with high quality grain types.

To reveal the mechanism of drought resistance of different resistant rice during germination period,Rice drought-sensitive materials(Calrose,Jingning 10,Shanxing 86)and drought resistance materials(Farry,Songjing 3,Ningjing 36)were studied on the effects of simulated drought stress(15% PEG-6000)on the growth index,physiological indexes and corresponding gene expression of different rice seeds.The results showed that under normal conditions,there were no significant differences in the expression levels of growth indicators and stress-related genes between drought-sensitive and drought-resistant cultivars.However,changes in physiological indicators were shown that there were no significant differences in the activities of superoxide dismutase(SOD) and peroxidase(POD),the contents of soluble sugar(SS) and hydrogen peroxide(H₂O₂) among different genotypes.The contents of malondialdehyde(MDA) and superoxide anion($\mathrm{O}_{2}^{\bar{.}}$) in the drought-sensitive cultivar Shanxing 86 were significantly higher than those in other materials,and the contents of catalase(CAT),proline(Pro) and soluble protein(SP) of drought resistant Ningjing 36 were significantly higher than those of other materials as well.Under drought stress,the relative germination potential(RGP),relative bud length(RSL),germination drought resistance index(GDRI)and vitality index(VI)of germinating seeds increased by 0.03—0.07 percentage,0.32—0.39 percentage,0.12—0.18 percentage and 92.41%—108.39%,respectively;MDA and reactive oxygen species($\mathrm{O}_{2}^{\bar{.}}$,H₂O₂) contents in germinating seeds of drought-resistant cultivars decreased by 2.54%—61.64%,19.60%—46.30% and 35.61%—62.02% respectively compared with drought-sensitive cultivars.The contents of osmotic regulating substances(Pro,SS,SP) increased by 5.93%—18.29%,1.08%—7.97% and 3.47%—6.03% respectively.The activities of antioxidant enzymes(SOD,POD, CAT) were increased by 17.29%—33.12%,15.24%—76.06% and 14.68%—18.61% respectively.The relative expression levels of OsP5CS,antioxidant enzyme synthesis genes (OsALM1, OsPOX1, OsCATC) were up-regulated by 2.66%—182.31% and 57.14%—513.27%,0.38%—109.06% and 63.39%—184.25% respectively.Comprehensive analysis showed that drought stress inhibited the germination of rice seeds and affected the physiological characteristics of seeds and the expression of corresponding genes during germination.Under drought stress,vigor index(VI),peroxidase(POD)and peroxidase synthesis gene(OsPOX1)are the key indicators affecting rice seed germination,whether it is drought-resistant or drought-sensitive materials.In addition to the above indicators,soluble protein(SP),proline synthesis gene(OsP5CS)and catalase gene(OsCATC)are other key indicators affecting drought-resistant materials.Relative shoot length(RSL),hydrogen peroxide(H₂O₂)and superoxide dismutase gene(OsALM1)are other key indicators affecting drought-sensitive materials.

In order to select a reasonable fertilization pattern suitable for high-yielding and high-quality production of rice stubble weakly glutenous wheat,this experiment was conducted with weakly glutenous wheat Ningmai 13 and Wanximai 0638 as the test varieties,with no fertilization(CK),conventional fertilization of compound fertilizer+urea(T1),slow-release blended fertilizer(T2),loss-control fertilizer(T3),humic acid compound fertilizer(T4),and wheat formula fertilizer(T5),under the same conditions of nutrient supply,the effects on dry matter distribution and transport,filling,yield and quality of weakly glutenous wheat were analyzed.The results showed that slow-release blended fertilizer and wheat formula significantly increased the post-flowering dry matter production,and increased wheat grain filling rate,effective filling days,and grain weight compared with conventional fertilizer application.The grain yield increased by 9.27%—24.30% and 11.64%—22.98% respectively compared with conventional fertilizer.Slow-release blended fertilizer 2 years two varieties than conventional fertilization treatment of nitrogen fertilizer agronomic efficiency increased by an average of 23.14%, 36.88%, wheat formula fertilizer two years two varieties than conventional fertilization increased by an average of 36.31%, 39.35%. Wheat formula fertilizer treatment of two wheat varieties for testing grain quality had reached the national standard of weak gluten wheat. In summary,wheat formula fertilizer can be used as one of the fertilization patterns for high-yielding and high-quality production of rice stubble weak-gluten wheat in the test area,or appropriately reduce the application amount of slow-release blended fertilizer as the fertilization pattern for high-yielding and high-quality production of rice stubble weak-gluten wheat.

To explore the role of Osp39 gene in the regulation of rice chloroplast protein import, the sequence of Osp39 gene and upstream elements in its promoter were searched and analyzed by using bioinformatics assay,and the homology,properties and structure of the OsP39 protein were also carried out.The tissue expression of Osp39 gene and subcellular localization of OsP39 protein were analyzed by quantitative PCR and transient expression in protoplasts,respectively.The results showed that the Osp39 gene was located on chromosome 5 of rice.There were 11 exons in the coding region of Osp39 gene,and its transcription product had no alternative splicing mode,so there was only one type of transcription product.The Osp39 promoter contained a variety of light-responsive and chloroplast regulatory elements such as I box and ATCT-motif.Transcriptional analysis of Osp39 gene also showed that the transcription level of Osp39 gene in green tissues such as leaf and leaf sheath was significantly than that in non-green tissue such as root and flower during seeding and flowering stages.OsP39 protein was stable and heat-resistant,which molecular weight was about 38.7 ku and theoretical isoelectric point was pH 8.64.There were a total of 361 amino acid residues in OsP39 protein,of which the content of glycine was the highest.The 245-271 amino acid residues formed a highly conserved L6 loop region,which belonged to the characteristic domain of the OMP85 protein family.Spatial structural analysis revealed that OsP39 was a β-barrel membrane protein rich in β-sheets.Subcellular localization analysis showed that OsP39 protein was localized at the rice chloroplast membrane.The above results indicated that Osp39 gene was a chloroplast membrane related gene,which was involved in the regulation of light response and chloroplast function in rice.

To screen out the stable reference gene for Real-time quantitative PCR under rapid cold hardening conditions,ten candidate reference genes from the transcriptome sequencing of Lissorhoptrus oryzophilus Kuschel were selected.Real-time quantitative PCR was used to obtain the expression levels of the selected candidate reference genes in adults under different rapid cold hardening conditions.The expression stability of the selected candidate reference genes was analyzed by ΔCt method,geNorm,NormFinder and BestKeeper softwares.ΔCt predicted the most stable candidate reference gene was RPS18.It was revealed that RPS18 and G6DPH were the most stable reference genes based on the geNorm analysis,while G6DPH, RPL13 and α-tubulin were the most stable reference genes based on the NormFinder analysis and BestKeeper analysis,respectively.The stability of RPS18 gene was relatively high based on comprehensive analysis. It was found that the expression level of LoTPS gene increased under rapid cold acclimation when RPS18 was used as an internal reference gene, and it was higher in all the cold acclimation treatments than control. Therefore, RPS18 was relatively stable and could be used as an internal reference gene under different rapid cold acclimation conditions. Low temperature stress promoted the up-regulation of LoTPS gene under rapid cold acclimation, and the expression level increased with the prolongation of cold acclimation time.

To further investigated the effect of different allelic variants of TaGAMyb-B genes in wheat on stem elongation, used the rice Agrobacterium transformation system,RT-qPCR,tissue section and cell tissue specific analysis to systematically study the function of the 84 bp InDel of TaGAMyb-B.The results showed that,in the over-expressed transgenic rice lines,transcript expression of TaGAMyb-B was detected in seeds,roots,stems and leaves;TaGAMyb-Bb-GFP transgenic seeds were more sensitive under the treatment of NaCl,GA and mannitol compared with TaGAMyb-Ba-GFP;the diameters of first,second and third stem inter-nodes,spike length and tiller number of TaGAMyb-Ba-GFP were significantly larger than that of TaGAMyb-Bb-GFP;and the analysis of cell tissue sections showed that the average thickness of the thick-walled tissue cells in the transverse sections of the transgenic TaGAMyb-Ba-GFP rice was significantly greater than that of the transgenic TaGAMyb-Bb-GFP event,the average length of thick-walled cells was extremely significantly shorter than that of transgenic TaGAMyb-Bb-GFP event.The above mentioned results indicated that the 84 bp deletion in TaGAMyb-B increased not only abiotic stress resistance and plant lodging resistance,but also spike length and tiller number in transgenic rice.

To further explore the biological function of rice polyembryo candidate gene OsPE,Oryza sativa ssp.Japonica cv.Nipponbare and Indica cv.Basmati 370 was taken as the research materials, and the mature leaves of the test materials under normal growth conditions were employed.Bioinformatics,RT-PCR,TA cloning,semi-quantitative,and qPCR were used to identify and analyze the splicers of OsPE.The bioinformatics analysis showed three kinds of variable splices of OsPE in Japonica rice and no variable splices in Indica rice.But the existence of three variable splices of the OsPE gene was identified in Japonica rice.Two new variable splice variants were found in Indica rice through RT-PCR amplification with specific primers,combined with TA cloning and sequencing verification.Subsequently,the semi-quantitative and qPCR results showed differences in the expression of the variable splices of the OsPE gene.Moreover,the expression intensities are as follows:OsPEc>OsPEa>OsPEb,the gene had the same expression trend in different rice varieties.Finally,the evolutionary analysis and functional prediction of the protein encoded by the OsPE gene showed that the OsPE protein was highly conserved in Gramineae,especially in Oryza L.(percent identity was higher than 99%).It needs to be further studied whether this gene was involved in regulating rice's stress response,cell division,and apoptosis but not the regulation of rice polyembryony production.To sum up,the OsPE gene was highly conserved in Gramineae,especially in Oryza L..This gene had the same splicing pattern in Japonica and Indica rice.Its variable splices had different expressions under normal growth conditions,but the expression trend was the same,OsPEc spliceosome dominate the function of the OsPE gene.It needed to be further studied whether this gene was involved in regulating rice's stress response,cell division,and apoptosis but not the regulation of rice polyembryony production.

Yuanjiang common wild rice(YP)is a germplasm material known as a living fossil in plants,which also has a large number of resistance(R)genes.Therefore,knowing the R genes in YP will help to apply different R genes to cultivated rice.Here,we identified the bacterial blight(BB)R genes in Yuanjiang common wild rice(YP),progeny of introgression lines(L214 and G252)and its susceptible parent,cultivated rice line 35(HX35).Meanwhile,the resistance of YP and its introgression lines to several Xanthomonas oryzae pv.oryzae (Xoo)strains was determined at the late tillering stage of rice.Under indoor control conditions,YP and its introgression lines showed resistance to 9 different Xoo strains(C1,C2,C3,C4,C5,C6,C7,C9 and PXO99^A),indicating that they had broad-spectrum resistance to BB.The results of bacterial blight resistance gene detection showed that YP contained homologous genes of Xa10,while HX35,L214 and G252 contained susceptible homologous genes of xa23.The sequence alignment results showed that the sequence of the effector binding element (EBE_AvrXa10) region of the disease resistance gene Xa10 was significantly different from that of the Xa10 promoter in YP. Similarly, the recessive susceptible gene xa23 was consistent with the effector binding element (EBE_AvrXa23) region of the xa23 promoter in HX35, L214 and G252. The qRT-PCR results showed that the immune responses in YP,HX35,L214 and G252 were activated after inoculation with strain PXO99^A,but Xa10 in YP and xa23 in HX35,L214 and G252 were not induced to be expressed.It is thus hypothesized that YP,L214 and G252 may contain new genes for resistance to bacterial blight.

To investigate the potential functions of DUF760s in rice growth and development,the genome-wide identification,classification,promoter sequence and expression profile analysis of the DUF760 gene family were performed.This research identified 6 and 8 members of DUF760 gene family in rice and Arabidopsis respectively by bioinformatics analysis.Phylogenetic tree analysis divided these members into two subfamilies,there were also some characteristic differences between the two subfamilies in protein conserved motif and gene structure.Multiple cis-acting elements responding to stresses and phytohormones existed in the promoter regions of rice DUF760 family genes.ABRE(abscisic acid response)element was present in the promoter sequence of all DUF760 family members,the promoter region of OsDUF760-1 possessed 9 abscisic acid(ABA)related response elements.The transcriptional expression level of OsDUF760-1 in rice was significantly down-regulated after ABA treatment,while OsDUF760-3 was significantly up-regulated.The expression change patterns of these two genes in rice after drought stress treatment were consistent with that after ABA treatment,which indicated that these two genes may participate in rice drought stress response through ABA signaling pathway,and play different roles.In addition to strong responses to ABA and drought stress treatments,members of rice DUF760 family also showed relatively strong expression changes in response to JA(Jasmonic acid),low temperature and M.oryzae treatments.

In order to improve blast resistance of the maintainer line Ruanhua B,to carry rice blast resistance genes Pi46 and Pi2 high-quality Indica H281 as the donor parent,Ruanhua B as recurrent parent,using marker-assisted selection(MAS)technology combined with pedigree breeding method,polymerization of two foreign genes with improved maintenance line Ruanhua B resistance,Ruanhua B was carried out on the characteristics of stable strain identification of resistance to rice blast,rice quality analysis,etc.Two BC₁F₆ populations,two BC₂F₅ populations and two BC₃F₄ populations with two homozygous target genes were obtained by backcrossing,multi-generation self-crossing and molecular marker detection.Field naturally induced identification showed that the improved lines of different backcrossing generations were resistant to rice blast.The sterility of backcross generation to sterile lines ranged from 52.7% to 100.0%.Agronomic traits and rice quality analysis showed that the improved lines basically conserved the main agronomic characters and rice quality characteristics of Ruanhua B.The results of SNP gene chip analysis showed that the background response rate of BC₁F₆ was 74.42%—77.77%,that of BC₂F₅ was 86.42%—87.75%,and that of BC₃F₄ was 92.27%—92.59%.Multiple resistance genes can be effectively polymerized by continuous backcross,self-cross and marker-assisted selection techniques to obtain a new maintainer line resistant to rice blast,and achieve rapid molecular improvement of maintainer line Ruanhua B.

To clarify the application potential of Neurospora crassa NC-3 strain on rice straw returning,a combination of indoor simulation and pot experiment were conducted to investigate the effects of NC-3 strain on degradation,cellulose,hemicellulosic,lignin,total phenolic acid content of rice straw,germination rate and seedling rate of rapeseed.The results showed that NC-3 strain could rapidly colonize on sterilized rice straw(full of mycelia and spores at 72 h).Compared with the sterile water,the degradation rate of rice straw in NC-3 strain was increased by 2.3,7.3 and 3.2 percentage points at 7,14 and 21 days,respectively.The contents of cellulose,lignin and total phenolic acid decreased with NC-3 strain by 2.0,10.7,10.4 percentage points,0.7,0.9,1.3 percentage points and 7.6%,6.9%,6.4%,respectively.The degradation effect of NC-3 strain on cellulose,lignin and total phenolic acid of rice straw mainly occurred in the first two weeks(0—14 days)of straw,and the degradation effect on hemicellulose gradually increased after 14 days of culture.Addition of rice straw significantly reduced the germination rate and seedling rate of rapeseed,and with the increase of straw dosage,the inhibition effect was enhanced,but NC-3 strain could significantly increase the germination rate and seedling rate of rapeseed(3.3 and 9.7 percentage points higher than sterile water in petri dish test,respectively).In summary,NC-3 strain could effectively accelerate the degradation of rice straw and the transformation of phenolic acids,and effectively improve the germination rate and seedling formation rate of rapeseed.

In order to study the effects of OsBAK1P,a precursor of Brassinosteroid insensitivity 1-associated receptor kinase 1,on the agronomic characteristics of rice.A target sequence fragment with a CDS fragment size of 651 bp was amplified from the rice panicle cDNA using the Zhonghua 11 japonica rice variety as the material according to the specific primers designed by the gene;the PTCK303-OsBAK1P overexpression vector and the PTCK303-OsBAK1P RNA interference vector were successfully constructed by restriction enzyme digestion and ligation methods;the Agrobacterium tumefaciens EHA105 strain was transformed into the correct expression vector plasmid,and the positive Agrobacterium tumefaciens clones were screened out by using CDS amplification primers;the callus of japonica rice cultivar Zhonghua 11 was infected by Agrobacterium tumefaciens genetic transformation to obtain transgenic plants;finally,compared to Zhonghua 11,two overexpressed and RNA-interfered T₁ transgenic plants with similar phenotypes were selected to measure and analyze the agronomic characteristics such as plant height,panicle length,and leaf angle,changes in root length and coleoptile length at the early stage of germination,and response to brassinolide(BL).The results showed that the plant height of OE-OsBAK1P transgenic rice was dwarfed,the panicle length was shorter,and the leaf angle decreased,meanwhile,the root length increased and the seedling length shortened after seed germination,and the leaves were not sensitive to BL.However,the plant height,panicle length and leaf angle of RNAi-OsBAK1P transgenic rice increased,meanwhile,root length shortened and seedling length increased after seed germination,and the leaves were sensitive to BL.To sum up,these results provide theoretical support for changing rice plant structure to increase grain yield and may provide a reference for further studies on other functions of OsBAK1 and its precursor OsBAK1P.

GlycosyltransferaseⅠ(GT Ⅰ)family is one of the glycosyltransferases,whose main functions involve the glycosyltransferase transfer of flavonoids and the synthesis of starch and sucrose.In order to reveal the role of GTⅠ gene family in the growth and development and high temperature tolerance of japonica rice, and to provide a basis for the functional study of GT Ⅰ gene family members in japonica rice,and provide ideas for rice variety improvement and high temperature tolerance. 30 members of GT Ⅰ gene family were identified by bioinformatics methods.The gene structure,physicochemical properties of proteins,chromosome location,gene evolution,phylogenetic relationship,conserved domain and protein three-dimensional structure modeling of members of GTⅠ genes in japonica rice were analyzed by bioinformatics.The results showed that 30 GT Ⅰ family members of japonica rice were distributed on 12 chromosomes of rice and the promoters of GT Ⅰ family members predicted abscisic acid response.The three-dimensional structure of family proteins was conserved and contained 6 β-folds and 7 α-helix.Transcriptome data and Real-time fluorescence quantitative analysis showed that most members of GT Ⅰ gene family responded to high temperature stress at 6 h after high temperature treatment.The expression level of OS-GT29 was continuously high.GT Ⅰ family was functionally similar in Arabidopsis thaliana and rice.

In order to solve the problem of the reduction of the migration of young rural labor force and the aging of the population,the enthusiasm for food crop production has been greatly reduced,and it is urgent to explore rice planting methods with less labor input and matching high-yield varieties.Through field trials from 2017 to 2019,two common and easy-to-promote planting methods were compared,and 14 early rice varieties and 12 late rice varieties were screened for easy purchase.The planting methods were simulated machine transplanting and machine direct seeding.Effects of different planting methods on the growth period,yield and dry matter weight of different early and late rice varieties.The results showed that direct seeding could shorten the growth period compared with transplanting.The average growth period of early rice direct seeding was shortened by 7 d compared with transplanting,and the average growth period of late rice was shortened by 8 d.The growth period of direct seeding had a smaller fluctuation range and more stable performance than transplanting.The annual average yield was significantly higher than that of transplanting,which was 29.71% higher in 2017,12.37% higher in 2018,and 7.15% higher in 2019,and it was found that the yield and dry matter accumulation at different periods were affected by the variety,the planting method and year had a very significant effect;through the linear regression covariance test,there was a positive correlation between the yield and the dry matter accumulation,which showed that the yield increases with the increase of the dry matter accumulation,and the coefficient of determination of the linear regression of the direct seeding method(R²)were higher than the transplanting method.A comprehensive comparison showed that the direct seeding method performs better in both the early and late rice planting methods,and the stable and high-yield(high-yield performance in the field in three years)that is matched with the direct seeding method is screened.The early rice variety Zhuliangyou 829(the yield fluctuation range of 6.02—10.90 t/ha),Yuliangyou 4156(6.49—10.22 t/ha),and stable and high-yielding late rice variety Wuyou 308(10.43—12.65 t/ha),the selected early and late rice varieties had moderate growth periods and can be effectively connected achieve high-yield planting of early and late rice.

In order to explore the effects of different long-term (36 a)fertilizer treatments on characteristics of soil acid buffering capacity at different soil layers (0—10 cm and 10—20 cm)under the double-cropping rice field in Southern of China,four different fertilizer treatments were set up:without any fertilizer input as a control(CK),chemical fertilizer alone (MF),rice straw and chemical fertilizer (RF),and 30% organic manure and 70% chemical fertilizer (OM).Soil acid neutralizing capacity(ANC),acid buffering capacity(ABC),instant acid buffering capacity(IAC),ammonium nitrogen($\text{NH}_{4}^{+}$-N),nitrate nitrogen($\text{NO}_{3}^{-}$-N)contents,and its relationship between soil acid buffering capacity and soil physicochemical properties were analysis.This result indicated that soil ANC,ABC and IAC at soil 0—10 cm and 10—20 cm layer in the double-cropping rice field with MF,RF and OM treatments were increased.The order of soil ANC,ABC and IAC at soil 0—10 cm and 10—20 cm layer in paddy field with all fertilizer treatments showed OM>RF>MF>CK.Compared with CK treatment,soil ANC and ABC at 0—10 cm and 10—20 cm layer in paddy field with OM treatment increased by 36.78%,33.18% and 18.67%,17.84%,respectively.Soil IAC at 0—10 cm and 10—20 cm layer in paddy field with OM treatment increased by 15.22% and 14.02%,compared with CK treatment,respectively.This result indicated that soil $\text{NH}_{4}^{+}$-N content at 0—10 cm and 10—20 cm layer in paddy field with MF treatment were significantly higher than that of RF,OM and CK treatments.Soil $\text{NH}_{4}^{+}$-N content at 0—10 cm and 10—20 cm layer in paddy field with MF treatment increased by 48.15% and 51.09%,compared with CK treatment,respectively.This result showed that soil $\text{NO}_{3}^{-}$-N content at 0—10 cm and 10—20 cm layer in paddy field with OM treatment were significantly higher than that of MF,RF and CK treatments.Soil $\text{NO}_{3}^{-}$-N content at 0—10 cm and 10—20 cm layer in paddy field with OM treatment increased by 204.73% and 161.94%,compared with CK treatment,respectively.Soil ANC,ABC,IAC,$\text{NH}_{4}^{+}$-N and $\text{NO}_{3}^{-}$-N contents at 0—10 cm layer were obvious higher than that of 10—20 cm layer in paddy field under the same fertilizer treatment condition.It had significantly positive correlation between soil ANC,ABC,IAC and soil organic carbon,total nitrogen contents,electrical conductivity in paddy field.Meanwhile,there had extremely significantly positive correlation between soil ANC,ABC,IAC and soil pH,cation exchange capacity in paddy field.As a result,it was effective practices for increasing soil acid buffering capacity at plough layer under the double-cropping rice field in Southern of China by combined application of rice straw or 30% organic manure with chemical fertilizer managements.

Direct seeding and brackish water irrigation represent an important way to alleviate the labor shortage and progressive water scarcity for rice production in the Yellow River Delta. However,the exact impact of these methods on the growth,yield and quality of rice is still unclear. The present study used a split-plot experimental design with irrigation as the main plot and cultivation methods as the subplot from 2019 to 2020. The experiment had two levels each of irrigation(F.Freshwater irrigation;B.Brackish water irrigation)and three seeding methods(D.Dry direct seeding;W.Wet direct seeding;T.Transplanting). The study identified wet direct seeding was conducive to enhance rice height,while dry direct seeding was beneficial for promoting leaf area per rice and dry matter per rice. And,the above agricultural traits were significantly reduced by brackish water irrigation. Brackish water irrigation decreased rice yield by reducing yield components. In 2019 and 2020,the rice yield of transplanting by freshwater irrigation was 749.93,713.58 kg/ha higher than dry direct seeding,although the yield was also higher than wet direct seeding,the difference was not significant. Furthermore,the yield of wet direct seeding was higher than transplanting under brackish water irrigation condition,the yield difference was also not significant. The processing quality,appearance quality and protein content by wet direct seeding were significantly higher than transplanting. And brackish water irrigation contributed to the reduction of processing quality,appearance quality and taste value. Brackish water irrigation combined with direct seeding significantly reduced the yield and quality of rice,lowering the taste value despite the elevated protein and amylose content. Thus,the selection and breeding of salt-tolerant rice varieties suitable for wet direct seeding should be enhanced in the future research.

In order to study the reasons for the differences of different types of rice under cadmium stress,it used the cadmium sensitive indica rice restorer line Changhui 891(CH891)and the cadmium tolerant japonica rice variety 02428 as materials,and selected the buds after seed germination,which were continuously treated with cadmium for 3 days and not treated with cadmium for RNA-Seq analysis using high-throughput Illumina HiSeq 4000 sequencing technology.A total of 539 524 490 valid read were obtained,the comparison rate with the reference genome was between 94.81% and 96.82%,and the GC content was above 49%.Through comparative analysis,a total of 7 204 differentially expressed genes(DEGs)were detected,among which 849 genes were specifically expressed in CH891(SCR3),676 genes were specifically expressed in 02428(RCR3),and 770 genes were expressed in both varieties(CCR3),but the expression level was different.The analysis of enrichment pathways of KEGG and GO showed that isoflavone biosynthesis,inositol phosphate metabolism,flavonoid biosynthesis and anthocyanin biosynthesis were significantly enriched in SCR3.Ribosome,regulation of autophagy and insulin resistance pathways were significantly enriched in RCR3.Alpha-linolenic acid metabolism,phagosome,limonene and pinene degradation and fatty acid degradation pathways were significantly enriched in CCR3.The results showed that after Cd treatment,the secondary metabolic process was mainly enriched in CH891,and the protein metabolism was mainly enriched in 02428.In conclusion,the metabolic pathways of CH891 and 02428 were different after Cd treatment,and the molecular mechanism controlling these metabolic pathways might be the main reason for the differences of cadmium stress in different rice varieties.

This study intended to investigate the dynamic shoot characteristics and differences of several super rice cultivars and provide theoretical guidance for super rice breeding and cultivation in the South China rice area.Four super hybrid rice combinations,two super conventional rice varieties,and two high-quality super-high-yielding traditional rice were selected as test materials and applied.We investigated the plant leaf morphology,dry matter weight per unit area,yield at the seedling stage,active tillering stage,secondary panicle branch differentiation stage,initial heading stage and mature stage.The results showed that five dynamic shoot indexes,such as plant height,average number of tillers per plant,leaf morphology,dry matter weight per unit area and yield components,had significant seasonal ecological characteristics.Moreover,except the leave tillering angles from the early and middle stages of growth and development,other key indicators displayed that the super hybrid rice combination was significantly higher than the super conventional rice varieties.In details,the number of effective spikes per unit area,total grains per spike,thousand grains weight,economic coefficient and yield per unit area were significantly higher in the hybrid rice combinations than in the conventional rice varieties;while the spike length and seed setting rate of the conventional rice varieties were extremely significantly higher than those of the hybrid rice combinations.So,the construction of wide adaptation super rice breeding demands early and fast seedling development,high biological yield at mid and late growth stage,and high harvest index at maturity.Meanwhile,conventional rice varieties need to cultivate early and fast development characteristics,improve biological yield,and increase thousand grains weight and total number of grains per spike appropriately as well as maintaining high seed setting rate.Hybrid rice combinations requires to improve seed setting rate.

In order to study the effects of straw returning on soil active organic carbon components and carbon cycle related enzyme activities in rice-rape rotation farmland of Chengdu Plain,we carried out 3-year straw returning field experiment(2017—2020),including no straw(CK),chemical fertilizer alone(NPK),50% straw returning and chemical fertilizer(SR1),100% straw returning and chemical fertilizer(SR2),200% straw returning and chemical fertilizer(SR3).We measured soil physical-chemical properties,soil organic carbon content(SOC),soil labile organic C fractions,carbon cycle related enzymes,and their correlations.The results showed that straw returning could effectively improve soil physical-chemical properties,soil available nitrogen,phosphorus and potassium contents.Compared with CK treatment,straw returning treatments significantly increased SOC,ROC,DOC,and MBC contents by 5.05%—8.55%,18.40%—36.80%,35.76%—66.93% and 27.20%—52.10%,respectively.In general,higher returning dosage resulted in higher C content.On the other side,compared with CK and NPK,straw returning treatments significantly increased soil cellulase,β-glucosidase,catalase,polyphenol oxidase.The activities of soil cellulase,β-glucosidase,and polyphenol oxidase under SR2 treatment were the highest,which were significantly higher than SR1 treatment by 16.25%,8.49%,and 14.69%,respectively.The catalase activity of SR3 treatment was the highest,which was significantly higher than that of SR1 treatment by 25.10%(P<0.05).There were significant positive linear correlations among soil SOC,labile SOC fractions,and carbon cycle related enzyme activities.Consequently,full straw returning has been proved of the most efficient way of improving active organic carbon components,carbon cycle related enzyme activities,and promoting the improvement of soil quality in rice-rape rotation farmland of Chengdu Plain.

Tillering stage and jointing—booting stage are important for the formation of panicle number and spikelets per panicle of rice,respectively.Nitrogen application affects the formation of panicle number and spikelet per panicle.Bacteria involve in soil nitrogen cycle.Two high-yield rice varieties,Y Liangyou 900 and Zaofengyou 69,were used to study the difference of soil bacterial number and community structure between tillering stage and jointing—booting stage,and the relationship between them and soil nitrogen,rice yield under two application ratios of nitrogen fertilizer(7:3 and 6:4 application ratios of basic tiller fertilizer to panicle-spikelet fertilizer).The results showed that there were significant differences in the structures of dominant bacterial groups in paddy soil between the tillering stage and jointing—booting stage,which were mainly Proteobacteria,Bacteroidetes,Chloroflexi and Acidobacteria.The relative abundance of Chloroflexi at the tillering stage was 6.16 percent points higher than that at the jointing—booting stage.The relative abundance of Acidobacteria at the tillering stage was 2.65 percent points higher than that at the jointing—booting stage.The relative abundance of Proteobacteria at the jointing—booting stage was 0.69 percent points higher than that at the tilling stage.The relative abundance of Bacteroidetes at the jointing—booting stage was 1.09 percent points higher than that at the tillering stage.The results of correlation analysis showed that rice yield was significantly negatively correlated with the number of soil bacteria at the tillering stage,but significantly positively correlated with the number of bacteria and total nitrogen content in the soil at the jointing—booting stage.There was a significant positive correlation between the number of effective panicles and the number of soil bacteria at the tillering stage.The number of spikelets per panicle was significantly positively correlated with the ammonia oxidation potential at the tillering stage and the jointing—booting stage.Redundancy analysis(RDA)showed that the bacterial community structures were affected by many factors.The contents of soil ammonium nitrogen and the ammonia oxidation potential were the main factors affecting the bacterial community structures at the tillering stage and the jointing—booting stage,respectively.The function prediction of FAPROTAX further indicated that the denitrification in the 7:3 treatment at the tillering stage was enhanced,especially in the soil of Y Liangyou 900.Therefore,increasing the number of soil bacteria at the tillering stage could enhance the number of effective panicles.Ammonia oxidation involved by soil bacteria at the jointing—booting stage can promote the increase of spikelets per panicle in rice.For the high-yielding rice varieties,Y Liangyou 900 and Zaofengyou 69 under different nitrogen application ratios,the formation of yield,effective panicle number and spikelets per panicle is closely related to soil bacterial number,community composition and ecological function.

In order to improve the blast resistance of Shuijing 3,an excellent food-flavor rice variety,CRISPR/Cas9 gene editing technology combined with gene chip technology were used to pyramid the R gene Pigm and the non-R gene bsr-d1 into Shuijing 3.Firstly,Bsr-d1 was selected as the target gene to construct a recombinant expression vector using the CRISPR/Cas9 gene editing system,and transformed into the excellent food-flavor rice Shuijing 3 by Agrobacterium-mediated method.The homozygous bsr-d1 mutant lines without T-DNA elements,including five mutation types as T insertion,G insertion,GA deletion,CGCA deletion and CGCAGA deletion,were screened out.The japonica line Jinyu 1 containing a broad-spectrum blast resistance gene Pigm was used as the gene donor parent to cross with the homozygous bsr-d1 mutant lines without transgenic components.The Pigm gene was introduced into bsr-d1 mutant lines by cross,backcross and self-cross combing molecular breeding chip to simultaneously perform Pigm gene and background-assisted selection.The improved lines SJ3-G1,SJ3-G2,SJ3-G3,SJ3-G4,SJ3-G5,which were homozygous for the disease resistance genes(carrying both bsr-d1 and Pigm genes)and whose background recovery rates were all above 96%,were finally obtained.The improved strains of Shuijing 3 displayed enhanced leaf blast resistance compared with the wild type in inoculated identification test using Magnaporthe grisea strain GUY11.After inoculation with M.oryzae,the POD activities in the improved strains of Shuijing 3 were significantly lower than that of the wild-type control,while the H₂O₂ contents were significantly higher than that of the wild-type control.The improved Shuijing 3 lines with blast resistance carrying both bsr-d1 and Pigm genes are obtained by CRISPR/Cas9 gene editing technology combined with gene chip technology.

In order to find out the regularities of formation of panicle grain characteristics of multi-panicle type and large-panicle type varieties to increase rice yield.The conventional field experiments method were conducted to use the multi-panicle type varieties Yueyou 9113(Y9113),the large-panicle type varieties Tianyouhuazhan(TYHZ)and Wufengyou T025(WT025)as test materials.To study the differences in carbon and nitrogen metabolism and yield composition of main stem,functional leaves and young panicles during the young panicle differentiation stages of multi-panicle type and large-panicle type varieties.The results showed that the activities of key enzymes in carbon and nitrogen metabolism(SPS,AMS,NR and GS)and soluble sugar and soluble protein content of the main stem,functional leaves and young panicles of large-panicle type varieties were higher or significantly higher than multi-panicle type varieties in the main young panicle differentiation stages.In the second branch and spikelet primordia differentiation stage,which the number of grains increased rapidly,the soluble protein content of functional leaves and soluble sugar content and GS activity of young panicles of Wufengyou T025 were significantly higher than Yueyou 9113 by 6.77%,35.07% and 20.10%,and the SPS activity of main stem and GS activity of young panicle of Tianyouhuazhan were significantly higher than Yueyou 9113 by 46.72% and 7.81%.In the meiotic stage of the pollen mother cell,which the spikelets are prone to degeneration and the number of grains decreases,the soluble protein content of functional leaves and soluble sugar content and soluble protein content of main stem of Wufengyou T025 were significantly higher than Yueyou 9113 by 9.88%,21.20% and 16.20%,and the soluble sugar content of main stem and SPS activity of functional leaves of Tianyouhuazhan were significantly higher than Yueyou 9113 by 14.67% and 28.55%.Under the conditions of this experiment,compared with the multi-panicle type varieties,the stronger carbon and nitrogen metabolism during the young panicle differentiation stage was one of the mechanisms of the large-panicle formation of the large-panicle type varieties.

In order to determine the appropriate nitrogen application level and irrigation mode for rice production in Hunan double cropping rice area,a randomized block design was adopted.Lingliangyou 942 and Lingyouhuazhan were used as early and late rice materials respectively.Three nitrogen application levels of N1-N3(150,120,0 kg/ha for early and late rice respectively)and three irrigation modes of W1-W3(water layer irrigation,wet irrigation and dry wet alternating irrigation for early and late rice respectively)were set.The effects of different water and fertilizer synergistic treatments on agronomic characters and yield of Double-cropping Hybrid rice were studied.The results were as follows:The increase of nitrogen fertilizer could significantly improve the SPAD value of rice, but the SPAD values of N1 and N2 were similar in early and late rice as a whole, while the irrigation method was W3, which could not only maintain a high SPAD in early and late rice, but also avoided late green and late ripening. Rice leaf area index (LAI) was directly proportional to the amount of nitrogen applied to a certain extent. The LAI values between N1 and N2 were similar in the whole growth period of early rice and the early growth stage of late rice, but N1 was higher than N2 in the late growth stage of late rice, while irrigation methods had little effect on the LAI value of early and late rice, mainly W3 was slightly higher. The increase of nitrogen fertilizer could significantly promote the accumulation of dry matter mass of rice. Except that the dry matter mass per plant of early rice at milk stage was N2 higher than N1 and the dry matter mass per plant of late rice at full heading stage was N1 higher than N2, the dry matter mass per plant of early and late rice at other stages was N1 and N2 similar, which showed that nitrogen reduction would not significantly have reduced the dry matter mass per plant of paddy rice on the whole. The irrigation method had little impacted on early rice and great impacted on late rice. The overall dry matter mass per plant of early and late rice increases better with W3, W2 followed. Increasing nitrogen fertilizer application could significantly improve the theoretical, actual yield and effective panicle number of rice, but they were similar in N1 and N2. Compared with the control group N3, the actual yield of early and late rice N1 and N2 increased by 53.21%-59.64% and 21.65%-32.68% respectively, indicated that the effect of nitrogen reduction and yield increase in early rice was obvious, and the poor effect of nitrogen reduction and yield increase in late rice was mainly because high nitrogen was not the nitrogen application level of conventional late rice.There was no significant difference between irrigation methods and yield and yield components. Under the cooperation of water and fertilizer,N2W2,N2W3 treatment could make early and late rice obtain higher leaf SPAD and LAI. Under the factors of dry matter accumulation, yield and yield components, the effect of N2W3 treatment was better for early rice, and N1W3 treatment was better for late rice. In conclusion, N2W3 treatment of early rice could not only met high yield, but also saved fertilizer and water;although N2W3 treatment of late rice performed better in SPAD and LAI, its dry matter accumulation and yield performance were lower than N1W3 treatment, so N1W3 treatment of late rice had obvious yield increasing effect. Therefore, from the perspective of economic and ecological benefits, under the alternative mode of dry and wet, the nitrogen application rate of early rice was 120 kg/ha and that of late rice was 150 kg/ha, which could give full play to the interaction effect of water and fertilizer. They had good yield increasing potential, which was more conducive to the growth and development of rice and increased yield.

In order to promote the breeding of long-grain japonica rice varieties,two knock-out vectors,pYLCRISPR/Cas9-GS3-RNA and pYLCRISPR/Cas9-GS3-GS9-RNA,were constructed with japonica rice varieties Dongfu 139,Longjing 31 and Dongnong 427,the genes of GS3 and GS9 were edited by Agrobacterium tumefaciens in vitro.In the end,GS3,GS9 and GS3,GS9 double-gene mutations without T-DNA elements were obtained in the T₂.The results showed that the grain length and 1000-grain weight of gs3 mutant plants of three varieties were significantly increased compared with those of wild type,grain width,seed setting rate and grain number per panicle did not change significantly,grain length of gs9 mutant increased significantly,and grain width decreased significantly,while 1000-grain weight,seed setting rate and grain number per panicle did not change significantly,and grain length of gs3gs9 mutant increased more than gs3 and gs9,at the same time,grain width decreased significantly,1000-grain weight increased significantly,while seed setting rate and grain number per ear did not change significantly.To sum up,three japonica rice varieties,Dongfu 139,Longjing 31 and Dongnong 427 were improved by using CRISPR/Cas9 technique,which accelerated the breeding process of new long-grain japonica rice varieties.

Reducing fertilizer application and increasing efficiency is of great significance to ensuring the sustainable development of agriculture.Research on the impact of new-type synergistic compound fertilizers on rice nutrient absorption and yield will help ensure the food security.Four treatments which were conventional compound fertilizer(CG),synergistic compound fertilizer(ZZ),conventional compound fertilizer reduction by 20%(80% CG),and synergistic compound fertilizer by 20%(80%ZZ)was set.The results showed that:Compared with the conventional compound fertilizer treatment,the synergistic compound fertilizer treatment could increase the fresh weight,plant height,SPAD value and root volume of rice at tillering stage,jointing stage,heading stage,filling stage and maturity stage.At the maturity stage,the fresh weight,plant height,SPAD value and root volume of rice plants treated with the synergistic compound fertilizer increased by 11.71%,1.29%,8.02% and 46.48%,respectively.The rice plant treated by the synergistic compound fertilizer reduced by 20% treatment increased by 2.29%,0.31%,3.70% and 4.09%,respectively.Compared with the conventional compound fertilizer treatment,the synergistic compound fertilizer treatment could increase the dry matter weight of stems and leaves and the dry matter weight of grains by 24.46% and 21.39%,respectively.The synergistic compound fertilizer treatment to increase the dry matter weight of rice stems and leaves and the dry matter weight of grain was 6.07% and 8.15%,respectively.Compared with the conventional compound fertilizer treatment,the nitrogen content of rice stems and leaves and the nitrogen content of grains under the treatment of synergistic compound fertilizer increased by 10.68% and 36.96%,respectively.The phosphorus content of rice stems and leaves increased by 26.51% and 11.24%,respectively.The phosphorus content of rice grains treated with synergistic compound fertilizer increased by 10.39%,and the phosphorus content of rice grains treated with synergistic compound fertilizer reduced by 20% decreased by 5.41%.Compared with the conventional compound fertilizer treatment,the potassium content in the stems and leaves of rice treated with the synergistic compound fertilizer increased by 19.91%,the potassium content in the rice grains decreased by 15.83%,and the potassium content in the stems and leaves of the synergistic compound fertilizer reduced by 20% treatment decreased 6.56%,the potassium content of grains increased by 0.62%.Compared with conventional compound fertilizer treatment,the yield of rice treated with synergistic compound fertilizer increased by 22.02% and the difference was significant.The yield of rice treated with synergistic compound fertilizer reduced by 20% increased by 1.12%.The rice panicle length,panicle number,grain number per panicle,1 000-grain weight and seed setting rate of rice of synergistic compound fertilizer were the highest among all the treatments.In summary,the synergistic compound fertilizer can improve the growth index of rice in each growth period,improve the nitrogen absorption,phosphorus absorption and potassium absorption of rice,and increase crop yield.Compared with conventional compound fertilizer,the 20% reduction treatment of synergistic compound fertilizer can realize the reduction of chemical fertilizer without reducing production,and it is worthy of further popularization and application.

In this regard,we carried out a research to study the dynamic changes of the weeds varieties and community composition under rice-duck farming.The experiment lasted for two years from the perspective of plant community ecology,four different treatment were adopted in the research,that was,not using of herbicide(CK),using herbicide(RH),not using herbicide under duck farming(DK),and using herbicide under duck farming(DH).Results showed that in the two years,DK reduced weeds by 47.00%,lower than 93.88% in RH and 100.00% in DH.DK also saw the formation of dominant weeds consisting of Echinochloa crusgalli (L.) Beauv, Monochoria vaginalis (Burm.f.) C.Presl, Cyperus rotundus L., and Leptochloa chinensis (L.) Nees in the full tiller stage,heading stage,and milk ripe stage.Dominant weeds respectively accounted for 71.20%,92.29%,and 94.03% of the total weeds in the above three stages.Monocotyledon weeds and gramineous weeds became dominant communities from full tiller stage to milk ripe stage,respectively accounting for 97.57% and 64.97% of the total weeds in the milk ripe stage.And the proportion of dicotyledon weeds and broadleaf weeds were 2.43% and 8.55%,respectively.The two-year experiment also saw the Shannon-Wiener Index and Simpon Index in DK treatment lower than those in CK and higher than those in RH.The Simpon Index and Pielou Evenness Index of DK and CK were not significantly different in heading stage and milk ripe stage,but DK had significant difference with RH.It indicated that although DK treatment could change the weeds community composition and diversity,its prevention and control on weeds was not significant.

To map QTLs that control cold tolerance at germination and bud stages,to explore the genetic mechanism,a recombinant inbred line(RIL)population was used as experimental material.The RIL population contained 189 lines derived from the cross between Caidao,a japonica rice variety that had strong cold tolerance and was adopted as the female parent,and WD,a indica rice variety that had weak cold tolerance and was used as the male parent.The QTLs that control cold tolerance at germination and bud stage were mapped between four phenotypic indexes and 978 Bin markers by IciMapping 4.2.The four phenotypic indexes included relative germination rate,average germination days,seedling rate and cold tolerance level.The results showed that two pairs of epistatic QTLs related to cold tolerance at bud stage were mapped.The LOD scores were 5.70 and 5.55 and the phenotypic contribution rates were 13.22% and 39.87%,respectively.In addition,five and five QTLs that were related to cold tolerance at germination and bud stage were mapped,respectively.These QTLs were located on chromosomes 1,3,5 and 8.The LOD score and phenotypic contribution rate of these QTLs ranged from 2.55 to 7.07 and from 6.41% to 17.17%,respectively.qLTG3 had the highest phenotypic contribution rate among the five germination stage QTLs and was also related to cold tolerance at germination stage.qCTP1-2 had the maximum of phenotypic contribution rate among the five bud stage QTLs.qCTB1,qCTP1-2 and qLTG8 had not been reported.The QTLs and epistatic QTLs detected will provide a reference for the genetic research and improvement of cold tolerance in rice.

To investigate the cultivation approach achieving robust seedlings and high yields of wheat in rice stubble,the effects of three tillage methods,including plow tillage followed by rotary tillage(PR),rotary tillage twice(RR),and no-tillage(NT),on the growth and physiology of main stem and tillers of wheat seedlings and their single spike yield at maturity were studied under the conditions of rice straw retaining with full amount.The results showed that PR increased the stems number per plant at the beginning of over-wintering by 1.5%,12.8%,respectively,compared with RR and NT,with significant differences(P<0.05).Leaf area and dry matter weight per plant under PR were 94 cm² and 787 mg,respectively,which were significantly higher than those under NT(P<0.05).Compared with NT,PR significantly improved activities of nitrate reductase(NR),glutamine synthase(GS),and glutamate synthase(GOGAT)of the top full expanding leaves in the main stem and the first,second,and third tillers(P<0.05).PR also significantly promoted the activities of diphosphate carboxylase(Rubisco),pyruvate phosphate dikinase(PPDK),triosephosphate isomerase(TPI),sucrose synthase(SS-Ⅱ),and sucrose phosphate synthase(SPS),and enhanced SPAD and soluble sugar content(P<0.05).And compared with NT,PR significantly increased the nitrogen content in seedling leaves of main stem,second and third tillers(P<0.05).Moreover,PR and RR increased leaf area and dry matter weight of the main stem and the first and second tillers.Therefore,compared with RR and NT,PR was more beneficial to the synergistic improvement of nitrogen metabolism,glucose metabolism,and light energy utilization at the seedling stage,increasing photosynthetic productivity and forming robust seedlings.The improvement of carbon and nitrogen metabolism and photosynthetic capacity by RR was higher than that by NT but was weaker than that by PR.There were no significant differences between PR and RR in the grain number per spike,single grain weight of the main stem(P>0.05),but they were significantly higher than those under NT(P<0.05).The grain number per spike in the first and second tillers under PR was significantly higher than that under RR and NT(P<0.05),but single grain weight and grain yield per spike of the first,second,and third tillers were not significantly different between PR and RR(P>0.05).In conclusion,PR could improve the activity of glucose and nitrogen metabolism and photosynthetic physiology of the main stem and the first and second tillers of wheat in rice stubble,resulting in the increases of the grain number per spike and the productivity per spike through forming strong seedlings.

Using rice variety Shendao 9 as an entry,a field experiment was conducted in 2019—2020 to study the effect of nitrogen application pattern and row spacing on canopy structure and yield of rice under split-plot design.The main plot treatments were zero nitrogen(A₀),farmer's pattern(A₁),low basal nitrogen(A₂),and basal nitrogen backward(A₃).The subplot treatments were conventional method(row spacing of 30 cm,B₁),reducing row spacing(row spacing of 25 cm,B₂),and narrow-wide row(row spacing of 40 cm+20 cm,B₃).The layer upon layer cut method was used to investigate the leaf area index(LAI),photosynthetic active radiation(PAR),photosynthetic characteristics of flag leaves,and grain yield of rice.The results showed that nitrogen application pattern and row spacing had extremely significant interaction effects on grain yield,the maximum value(9.85 t/ha)appeared in A₃B₂.Compared with A₁ and A₂,the effective spikelets per unit area,kernel-setting rate,net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of A₃ increased by 4.31%—10.55%,2.87—4.09 percentage points,4.84%—9.12%,14.08%—15.71% and 11.33%—15.83%,respectively.Meanwhile,rice obtained higher interception rate of PAR,population leaf area index under A₃.Compared with B₁ and B₃,the spikelets per unit area,and population leaf area index(LAI)of B₂ increased by 7.57%—9.97% and 4.29%—20.43%,respectively.And interception rate of PAR of B₂ was 88.99%.Given the results of grain yield,PAR,and photosynthetic characteristics in rice of two years,it could be concluded that the basal nitrogen backward pattern combined with 25 cm row spacing could enhance spikelets per unit area,kernel-setting rate,1000-grain weight,improve the population structure and obtain higher yield.

In order to explore the effects and mechanism of grain filling regulators on inferior spikelets filling of large panicle rice varieties,large panicle rice variety Jiaoyuanyou 216 was selected as material and an open field experiment was conducted by spraying exogenous grain filling regulators(Helifeng and Xinmeizhouxing)at heading stage.Meanwhile,endogenous hormone contents,expressions of filling-related miRNAs and their targets,and genes encoding filling-related proteins and sucrose-starch metabolism key enzymes were measured.The results should that the two grain filling regulators of Helifeng and Xinmeizhouxing significantly increased the yield of Jiaoyuanyou 216,the 1000-grain weight,filling rate and initial grain filling potential of inferior spikelets.Specifically,compared with the control(spraying water),the 1000-grain weight of inferior spikelets increased by 16.07% and 15.89%,respectively.Content of IAA in inferior spikelets increased significantly at 9,15,21 d after flowering,and the content of Z+ZR increased significantly at 9,21 d after flowering.Under Helifeng treatment,expressions of miR167a-c,miR167d-j and miR1432 were significantly down-regulated at 6 d after flowering,OsGF14b and OsGF14f were significantly down-regulated at 12 after flowering. What's more,expression of OsGLP3,a gene encoding germin-like protein was significantly up-regulated at 6 d after flowering,and expressions of sucrose-starch metabolism key enzyme related genes were significantly up-regulated at 6,12 d after flowering.However,under Xinmeizhouxing treatment,expressions of miR167a-c,miR167d-j,miR1432 were significantly down-regulated at 6 d after flowering,and expressions of OsGF14b and OsGF14f were significantly down-regulated at 12 d after flowering.More importantly,expressions of OsGLP3 and sucrose-starch metabolism key enzyme related genes were significantly up-regulated at 6,12 d after flowering.Correlation analysis results showed that the filling rate of inferior spikelets was significantly negatively correlated with the expression of miR1432 and OsGF14f,while was significantly positively correlated with the content of IAA.Therefore,Helifeng and Xinmeizhouxing may regulate the expressions of filling-related miRNAs and their targets,as well as the genes of filling-related proteins and sucrose-starch metabolism key enzymes in the pre-and mid-filling period and increase the content of IAA and Z+ZR to promote inferior spikelets filling.

In order to explore the changing law of dry direct-seeding rice quality under different organic fertilizer treatments,this experiment was conducted from 2018 to 2020.Longjing 31 was used as the test material.Treatments includes:zero fertilizer(N0),conventional fertilization(NPK),Biochar+conventional fertilization(OF1),seaweed bio-organic fertilizer+conventional fertilization(OF2),Jishiwang bio-organic fertilizer+conventional fertilization(OF3),attapulgite organic fertilizer+conventional fertilization(OF4).Changes in the processing quality,appearance quality,nutritional quality,and cooking and eating quality of dry direct-seeding rice were investigated.Compared with NPK,the head rice percentage of OF1,OF2,OF3,OF4 increased by 2.64 ,1.78,1.06,2.53 percentage points,respectively.The chalkiness degree of OF2 was the highest(1.82%),which was 0.11 percentage points higher than that of NPK.However,the chalkiness degree of OF1,OF3 and OF4 were lower than that of NPK,with an average decrease of 0.26,0.41,0.51 percentage points,respectively.There was no significant difference in grain length,grain width and length width ratio among the treatments.From 2019 to 2020,compared with NPK,organic fertilizer treatment increased protein content,but decreased amylose content;the protein contents of OF1,OF2,OF3 and OF4 were 8.99%,9.13%,9.08% and 9.16% respectively,which were 0.54,0.68,0.63,0.71 percentage points higher than those of NPK;the amylose content of OF1,OF2,OF3 and OF4 decreased by 0.20,0.64,0.69,0.38 percentage points,respectively;compared with NPK,the application of organic fertilizer at the initial stage could improve the luster,taste,flavor and taste value of dry-direct seeding rice,but long-term application of organic fertilizer would lead to poor cooking and eating quality;from 2019 to 2020,the average taste value of NPK treatment was 72.70,compared with NPK,OF1,OF2,OF3 and OF4 reduced the aroma,luster,taste,flavor and taste value of dry direct-seeding rice by 5.53%,6.40%,3.71% and 3.23%,respectively,but organic fertilizer increased the integrity of rice.In conclusion,long-term application of organic fertilizer can improve the processing quality,appearance quality and nutritional quality of dry direct-seeding rice,but it is not conducive to the formation of cooking and eating quality and reduce amylose content.

To explore the effects of basic application depth of chemical fertilizer on its utilization rate, rice growth and nutrient uptake. Five treatments including no fertilization(T1), and basal fertilizer application depth of 0(T2), 5(T3), 10(T4)and 15 cm(T5)were set up to study the effects of basal fertilizer application depth on rice yield and fertilizer use efficiency. The application depth of basal fertilizer had no significant effect on the leaf biomass of rice at different growth stages, but had significant effect on the stem biomass at mature stage. The stem biomass was significantly increased when the basal fertilizer was applied at 0 and 5 cm depth, and significantly decreased at fertilizer application depth of 10 cm and 15 cm at mature stage, and significantly lower than that of basal fertilizer application on soil surface(P<0.05);The uptake of N, P, K of rice leaf at different growth stages changed not significantly with basal fertilizer application depth, but the N, P and K uptake of rice stem at mature stage was significantly different due to basal fertilizer application depth(P<0.05);The N and K harvest index increased to the maximum at fertilizer application depth about 10 cm and the decreased, and was significantly correlated with basal fertilizer application depth(P<0.05). The application depth of base fertilizer with the largest nitrogen harvest index was 10.5 cm, while which of the largest potassium harvest index was 7.0 cm. The effect of basal fertilizer application depth on rice stem growth and nutrient absorption was greater than that on rice leaf. Basal fertilizer applied within an appropriately depth had positive effects on rice yield and fertilizer use efficiency. Considering the rice yield and element utilization, the depth of basal fertilizer applied within 7.0-10.5 cm was more conducive to improve the rice yield and fertilizer utilization.