In order to explore the photosynthetic physiological response mechanisms of three summer maize varieties (Xundan 20, Jinbei 288 and Dika 667) which were commonly cultivated in arid and semi-arid areas to drought stress, these three varieties were treated under different drought stresses (including non-drought treatment (CK), light drought (LD) and heavy drought (HD)). Responses of net photosynthetic rate to light intensity (Pn-PAR) and net photosynthetic rate to intercellular CO₂ concentration (A-Ci) were estimated by the portable photosynthesis system Li-6400, and responses of chlorophyll fluorescence parameters to light intensity were measured by portable modulation chlorophyll fluorescence meter MINI-PAM, respectively. The results were as follows. As for all these three varieties, the response modes of Pn and stomatal conductance (Gs) to PAR were similar among these three maize varieties, and the responses of Pn to Gs shifted to left along the drought stress gradient. The initial chemical efficiency (CE) and photosynthetic capacity (Amax) were significantly lower under heavy drought treatment than under the other two treatments for each of the three varieties. Compared with the results under CK treatment, the non-photochemical quenching coefficient (qN) and the quantum yield of the regulatory energy dissipation (Y (NPQ)) were lower and the quantum yield of non-regulated energy dissipation (Y(NO)) was higher under LD or HD treatment for the two varieties of Jundan 20 and Dika 667; and the photochemical quenching coefficient (qP) was lower under HD treatment for the variety of Jinbei 288. Compared with the results under CK treatment, the maximum net photosynthetic rate (Pmax) and initial quantum efficiency (AQY) were a little higher under LD treatment for the variety of Jinbei 288. Compared with the other two varieties, the Pmax and AQY showed higher tolerance to drought stress by keeping relatively lower qQ and lower Y(NO) for the variety of Jinbei 288, and these results not only showed the greater tolerance of Jinbei288 to drought stress, but also provided reference for the screening of crop varieties for drought tolerance.

In order to study the function of pollen lethal gene ZmAA1 and create tansgenic male sterile materials. ZmAA1 and its specific promoter Pg47 were found according to GenBank,designed to plus restriction endonuclease on the downstream and inserted them into an cloning vector puc57,construction of vector pCAMBIA3300-Pg47-ZmAA1-35S-bar used traditional construction methods digested connection.A maize inbred line Zheng 58 was infected by Agrobacterium tumefacfaciens with the vector pCAMBIA3300-Pg47-ZmAA1-35S-bar, 94 PPT-resistant seedlings were obtained and 47 plants were PCR positive.The pollen sterility in greenhouse RT-PCR assay for gene bar in the transgenic plant leaves and immuno strip test suggested that pollen lethal gene ZmAA1 had been integrated into the maize genome,and protein was expressed.

Drought stress has a serious effect on the growth and development of maize,which leads to a decrease of maize yield.Purple acid phosphatase is a phospholipase protein involved in many physiological and biochemical functions of plants.In order to further study the role of purple acid phosphatase family genes in the process of stress resistance of maize,this paper explored the response mode of ZmPAP26b gene under drought stress,and Real-time fluorescence Quantitavive analysis was used to analyze the relative gene expression in different maize inbreeding lines under simulated drought conditions;ZmPAP26b(GenBank:NC_050104.1)was cloned from maize,and PAP genes in Zea mays,Arabidopsis thaliana,Oryza sativa L.,Triticum aestivum L.,Sorghum bicolor and Brachypodium distachyon were identified and bioinformatic analysis was performed.Meanwhile,prokaryotic overexpression strains were constructed for functional verification.The results showed that the expression of this gene decreased in drought tolerant materials and increased in drought sensitive materials under drought stress.The CDS length of this gene was 1 431 bp,encoding 476 amino acids.A total of 228 PAP genes were found in six species,divided into 4 subfamilies by phylogenetic analysis.The 19 PAP genes in maize were distributed on 9 chromosomes and had similar conserved domains.Analysis of promoter cis-acting elements showed that they contained elements responding to drought and hormones.Prokaryotic expression experiments showed that the growth of strains containing the recombinant plasmid pET28a-ZmPAP26b was inhibited compared with non-loaded strains under 10% PEG-6000 and 15%PEG-6000 simulated drought stress.In summary,it is speculated that ZmPAP26b is negatively regulated under drought stress.

Based on the long-term located fertilization experiment of Laiyang, Shandong Province, China, began in 1978, to study the transport and accumulation characteristics of nitrate nitrogen and ammonium nitrogen in the Fluvo-aquic soil and its relationship with the summer maize yield.The test set organic fertilizer(M), nitrogen fertilizer(N)2 factors, 3 levels, 9 treatment;3 levels of organic fertilizer(M):M₀(0 t/ha), M₁(30 t/ha), M₂(60 t/ha), and 3 levels of nitrogen fertilizer(N):N₀(0 kg/ha), N₁(138 kg/ha), N₂(276 kg/ha).After summer corn harvest in 2014 and 2015, the contents of nitrate nitrogen and ammonium nitrogen in soil 0-20, 20-40, 40-60, 60-80 and 80-100 cm were measured respectively, the accumulation of nitrate nitrogen, ammonium nitrogen in different soil depth of 0-100 cm and the summer corn yield were calculated.The results showed that the amount of nitrate nitrogen, ammonium nitrogen and its accumulation amount in soil could be improved by applying organic fertilizer or nitrogen fertilizer.In the 0-100 cm soil layer, the vertical migration trends of nitrate nitrogen of different treatments were different, but the vertical migration trend of ammonium nitrogen were basically the same.Compared with chemical fertilizer, application of organic fertilizer could slow nitrate to the deep soil leaching, but both of ammonium nitrogen to influence the trend of migration in deep soil was not obvious.Long-term application of organic fertilizer, nitrogen fertilizer on nitrate nitrogen, ammonium nitrogen accumulation amount of the impact of extremely significant level, there was extremely significant interaction effect on the accumulation of nitrate nitrogen in soil.Compared with the M₀N₀(CK), the accumulation of nitrate nitrogen and ammonium nitrogen in the addition of fertilization treatments were significantly respectively increased by 112%-396% and 69%-259% at P<0.05.In 0-20, 0-40, 0-60, 0-80, 0-100 cm in each soil layer, the nitrate nitrogen accumulation and the ammonium nitrogen accumulation had different linear relationship with summer maize yield.Research showed that rational application of organic and inorganic fertilizers could reduce the accumulation of nitrate nitrogen and ammonium nitrogen in soil and the leaching, and it is advantageous to improve the yield of crops, maintain the stability of the soil ecosystem, promote the sustainable development of agriculture and protect the groundwater resources.

The objective of this study was to investigate the transcriptome differences after and before high temperature stress during maize anthesis stage, and to explore the key genes and proteins which are contributed to the high temperature resistant. The pollen activities of maize inbred lines Chang 7-2 and Zheng 58 were detected by Ampha^TM Z30 pollen activity analyzer (Amphays, Switzerland), firstly. RNA-sequencing, construction library and quality assessment were carried out for two periods before and after high temperature treatment using the Illumina Hiseq2000^TM sequencing platform, then the sequencing results were analyzed by bioinformatics. The differential expression genes (DEGs) were analyzed using edegR software. Key different expression genes and proteins with high temperature resistance were analyzed by VENN mapping, GO functional enrichment, KEGG pathway method and transcription factors analysis.The pollen activity of Chang 7-2 grown in normal condition was 42.89% and the pollen activity which was treated by high temperature during anthesis stage was 24.37%. The pollen activity of Zheng 58 which was grown in normal condition was 64.83% and the pollen activity treated by high temperature was 35.57%. The results showed that 4 176 significant DEGs were detected in Chang 7-2 inbred under normal growth condition and high temperature treatment. 5 487 significant DEGs were detected in Zheng 58 inbred under normal growth condition and high temperature treatment. KEGG pathway enrichment analysis showed that 2 062 differentially expressed genes in Zheng 58 were enriched in 399 related pathways. KEGG pathway enrichment analysis showed that 1 943 DEGs in Chang 7-2 were enriched in 352 related pathways. A total of 55 transcription factor families were obtained by the transcription factor analysis, of which 45 transcriptional factors contained more than 10 differentially expressed genes. In conclusion, Comparing the RNA-sequencing after and before high temperature treatment of Chang 7-2 and Zheng 58, many DEGs were obtained. The differences of response mechanisms between Chang 7-2 and Zheng 58 to anthesis high temperature stress were comparatively analyzed. The three gene families (Hsfs, IAA and PIP₂) and the Hsps proteins are playing significant roles in the regulation of high temperature stress in maize.

In order to improve the nitrogen use efficiency and corn yield during the whole growth period of maize, it provides a reference for the high-yield nitrogen fertilizer operation model of maize in Heilongjiang Area. Ratio (CK:blank control; T1:50% base fertilizer+50% flowering fertilizer; T2:30% base fertilizer+40% jointing fertilizer+30% flowering fertilizer; T3:20% base fertilizer+60% jointing fertilizer+20% flowering fertilizer; T4:10% basal fertilizer+60% jointing fertilizer+30% flowering fertilizer) on the change of soil inorganic nitrogen content, nitrogen balance, nitrogen accumulation at different growth stages, nitrogen use efficiency and corn yield. The results showed that compared with the control group, T2, T3, and T4 effectively increased the inorganic nitrogen content of the soil plow layer during the filling stage and the mature stage; in terms of nitrogen balance, T2, T3, and T4 were significant difference than the T1 treatment. Reduced the apparent nitrogen loss, of which T4 apparent nitrogen loss was the lowest; compared with T1, reducing the ratio of nitrogen to topdressing significantly increased the nitrogen accumulation during the flowering-maturity period, and the nitrogen accumulation during the filling-maturity period T4 was the highest treatment; compared with T1, T2, T3, and T4 significantly increased the nitrogen absorption and utilization rate, agronomic utilization rate and partial productivity of maize, and the increase ranges was 16.66%-22.47%, 17.80%-35.76%, 4.93%-9.90% (Xianyu 335) and 6.55%-24.46%, 8.23%-36.94%, 2.02%-5.44% (Tiannong 9); reducing the ratio of nitrogen fertilizer to topdressing (T2, T3, T4) yields significantly higher than the traditional nitrogen application treatment T1, T3 had the highest yield, which was 9.90% (Xianyu 335) and 8.86% (Tiannong 9) compared with T1. In summary, under the experimental conditions, when the total nitrogen application rate was 210 kg/ha, 20% basal fertilizer+60% jointing fertilizer+20% flowering fertilizer was the best nitrogen basal dressing ratio.

In order to study the effects of loss control and ordinary fertilizers on nutrient accumulation and growth and development of summer maize,field experiments were conducted at the Xinji experimental station of Agricultural University of Hebei during 2014-2015.Maize morphology and physiology characters and nutrient uptake efficiency were studied using maize hybrid Zhengdan 958 as material.The results showed that with the same nutrient amount (N 144 kg/ha,P₂O₅ 72 kg/ha,K₂O 72 kg/ha) of loss control and ordinary fertilizer applied,there were significant changes on maize growth and development,dry matter accumulation and nutrient accumulation,and the effects of loss control fertilizer treatment were significantly better than those of ordinary fertilizer.Compared with ordinary fertilizer,the 1 000 grains weight,dry matter and yield of maize of loss control fertilizer could be increased by 12.3%,12.8% and 6.9%,respectively.The content of nutrient elements in organs of loss control fertilizer treatment was higher than that of the ordinary fertilizer.Maize leaf area index and photosynthetic rate at kernel filling stage were enhanced by loss control fertilizer treatment.Stalk thickness and puncture resistance of basal internodes of loss control fertilizer treatment maize were also enhanced,so the lodging resistance ability was increased.As a new type of fertilizer,loss control fertilizer would play an important role in improving the yield of maize,increasing the efficiency of fertilization and protecting the environment.

In order to explore the effects of nutrient expert (NE) management on nitrogen (N) use efficiency and soil organic carbon (SOC) sequestration in the wheat-maize rotation system and improve its management practices, a long-term experiment was set up in 2009 to compare NE management with farmer's practice (FP) management. Through 9-years experiment, the crop yield, N use efficiency, SOC content, SOC sequestration rate and SOC sequestration efficiency were measured and analyzed. The advantages of long-term NE management in wheat-maize crop rotation system were evaluated. The results showed that long-term NE management reduced the amount of N fertilizer application rate, compared with FP management, but maintained the crop yields (no significant difference with FP). Compared with FP management, the average accumulative recovery efficiency of N, agronomic efficiency of N, and partial productivity of N in NE management system increased by 7.4 percentage points, 39.7%, and 28.4% in maize production system, and increased by 8.0 percentage points, 28.9%, and 32.8% in wheat production system, respectively After 9-years experiment, both NE and FP increased the SOC contents, with NE management increased faster than FP. The annual SOC contents rise rates of NE treatment in 0-5 cm, 5-10 cm and 10-20 cm soil profile were 0.28, 0.27, 0.34 g/(kg·a), respectively, which were 7.7%, 68.8% and 126.7% higher than those of FP treatment. The average annual carbon input of NE and FP treatment from straw returning were 8.5, 8.7 t/(ha·a), respectively, and the SOC sequestration rates were 1.35, 0.68 t/(ha·a),respectively, and the SOC sequestration efficiencies were 18.6% and 0.4%, respectively, which shown a significant difference. NE management could improve N use efficiency and increase SOC sequestration. Long-term NE management is one of the important measures for fertilizer saving, efficiency strengthen and SOC pool richen in wheat-maize rotation system. It would play a crucial role in ensuring food security and realizing agriculture green development.

A Receptor-like kinase(RLK)gene, OsSIK1,plays important roles in drought stress-tolerance in rice,through the activation of the antioxidative system.To make maize plants have much more drought resistance genes and further to obtain drought tolerance maize germplasm.In this study, OsSIK1 gene of rice was transformated into maize inbred Zheng 58 plants by pollen-mediated method.First,transgenic plants in T₁,T₂ and T₃ were detected by Kanamycin resistance screening,PCR and Southern Blotting,transgenic plants were obtained from T₁ and pure transgenic lines was obtained from T₃.Next,drought resistance analysis to transgenic maize plants and non-transformation control plants were conducted under the condition of 16.1% PEG drought stress.The results showed that compared with non-transgenic plants,the seedling leaf relative water content,chlorophyll content and SOD activity of transgenic plants were increased by 7.4%-19.8%,11.3%-106.9% and 45.8%-93.4%,respectively;furthermore,the relative conductivity and MDA content were decreased by 35.4%-58.1%,and 25.7%-50.4%,respectively.All the physiological indexes under the drought stress proved that transgenic OsSIK1 gene improved the drought resistance of transgenic maize plants,further analysis found that there were significant differences on drought tolerance between 5 transformed lines and their control groups,and their performance of field were superior to that of non-transgenic maize seedlings.At last,5 transgenic maize inbred lines were obtained,which suggested that genetically modified maize has improved the drought resistance by introducing foreign OsSIK1 gene of rice.

In order to explore the effect of grain size and sowing depth on emergence and seedling growth,determining suitable grain size and sowing depth in mechanization of summer maize production of Southwest Hilly Area.In the split-plot design,using Zhenghong 505 as the test material,3 kinds of grain size was assigned to the main plot,and 3 sowing depth(2,6,10 cm) to the subplot,emergence rate of maize,seedling quality,yield and yield components have been investigated in drought condition.The results showed that compared with small grain,large grain had higher emergence rate,the seedling was more haleness and grew better in drought,and there was a certain effect of increasing yield ultimately;Shallow sowing(2 cm) was conducive to the emergence,and the growth vigor of the seedlings of 6 cm sowing depth was best just when emerging,then the 10 cm depth of the seedling grew gradually strong,and obviously better at the 5 leaf period(large and medium grain)-7 leaf period(small grain) than shallow sowing treatment,which also showed a certain increase in yield.Therefore,in the dry land or dry season,choosing large grain and suitable sowing depth in maize production can effectively better sthong seedlings,improve the resistance of drought,and achieve the purpose of producing income insurance.

CorA/MRS2/MGT-type magnesium ion transporters play an important role in maintaining magnesium homeostasis in plants.In order to investigate the function of ZmMGT10 gene which is a maize CorA/MRS2/MGT-type magnesium ion transporter and expression is induced by magnesium deficiency,we constructed the overexpression vector of ZmMGT10 and transgenic Arabidopsis plants were obtained.Compared with wild-type plants,transgenic Arabidopsis plants grew more vigorously than wild-type plants under low Mg conditions,exhibited by longer root length,higher plant fresh weight and chlorophyll content.Further analysis indicated that the roots and shoots of transgenic plants had higher magnesium accumulation than wild-type plants under low magnesium condition.Furthermore,the roots of transgenic plants had enhanced magnesium uptake ability than wild-type plants.The results suggested that overexpression ZmMGT10 in Arabidopsis could enhance the resistance ability of transgenic plants to magnesium deficiency stress.

In order to investigate the molecular mechanism of Mu gene transfer in sweet corn mutant, the flanking sequence of the insertion site of Mutator gene was isolated by Mu-AFLP method, and the authenticity of transposon insertions was verified by a pair of specific primers P1 and P2 designed according to the extension of the flanking sequences.Meanwhile the genetic biological information of the insertion site was analyzed.The results showed that the flanking sequence was 299 bp, which was located on the third chromosome.The full length of the mutant gene was 5 746 bp, encoding 592 amino acid.The theoretical molecular weight of the encoding protein was 67.5 kDa, the hydrophobic amino acid content was 42.06%, which had 10 transmembrane.It belonged to hydrophilic membrane protein.This result laid a foundation for the better use of Mutator to create new germplasm of sweet corn and it was very important for the development of endosperm and starch synthesis in maize.

The purpose of this study was to explore the effects of different drought stress levels on maize growth traits and yield in the semi-arid region of Northeast China, and to lay a theoretical foundation for further research on the physiological mechanism of maize drought resistance.Three kinds of maize varieties with different drought tolerance were selected and five water gradients of normal water supply(CK), light drought(LS), moderate drought(MS), severe drought(SS)and lethal(S)were set at maize jointing, tasselling and filling stages, respectively. The effects of different drought stress on the growth traits and yield related indexes of three maize varieties were comprehensively analyzed. The plant height, ear position and dry matter weight of maize decreased with the increasing of drought degree, but the stem diameter had no significant difference with the increasing of drought degree. The plant height, ear position and dry matter accumulation of maize variety Jinqing 707 was the highest, followed by Nendan 19 and Fudan 16. During tasselling stage, the spike characters of maize changed most obviously under drought stress, and the maize yield was the lowest under severe drought, and no yield under continuous drought.Under the same drought degree, the worse the drought tolerance of maize varieties, the greater the yield reduction. The specific performance of maize yield is Jinqing 707 > Nendan 19 > Fudan 16.A comprehensive analysis of multiple indicators shows that tasselling stage is the key period of water requirement of maize, which is easily affected by drought stress. At the same time, it is pointed out that drought stress or serious degree of drought stress in tasselling stage is the main factor leading to the decrease of maize yield.

NRL(NPH3/RPT2-Like)is a type of light-responsive protein unique to plants and plays a vital role in the phototropic signal pathway. To reveal the NRL gene maize genome's characteristics and expression,we analyzed them using bioinformatics methods combined with qRT-PCR technology. The property,structure,evolution of their encoded proteins,and growth period tissue expression and stress expression were analyzed. 31 ZmNRL genes identified were located in nine maize chromosomes,encoding protein amino acids 464-749 aa,which predicted to have chloroplast,nuclear and cytoplasmic locations. According to protein conservation,ZmNRL family was divided into four categories. Their gene structure also presented certain conservation,the most contained four exons. Analysis of the cis-elements of gene promoters revealed a large number of abscisic acids,jasmonic acid,light response,and anti-oxidation elements,among which G-box and Sp1 were two types of light-related elements. The expression of ZmNRL family genes in tissues during the growth period showed a temporal and spatial specificity,and the majority expression level was not high. Only ZmNRL2,ZmNRL4,ZmNRL24,and ZmNRL29 highly expressed. Furthermore,the characteristic modules were produced based on the data of the tissue co-expression genes. And the GO enrichment analysis of a particular leaf growth module containing six ZmNRL genes,mainly associated with the plastid organization biological processes and rRNA binding molecular functions. The expression of ZmNRL5,ZmNRL7,ZmNRL12,and ZmNRL19 genes were analyzed by qRT-PCR under salt,drought,high temperature,and Rhizoctonia solani inoculation treatments. The results showed that ZmNRL12 was significantly up-regulated in maize seedlings treated with high temperature,while ZmNRL5,ZmNRL7 and ZmNRL19 genes were down-regulated in drought,salt and pathogen treatments. In summary,31 ZmNRL genes were identified in the maize genome. They not only had apparent specific tissue expression but also participated in biotic and abiotic stress responses.

bZIP transcription factors are widely found in plants and play an important role in regulating plant growth and development and abiotic stress response.In order to explore the functional role of bZIP transcription factor in maize drought stress response,transcriptome sequencing technology was used to analyze the expression changes of transcription factors in maize seedlings treated with drought stress for 5 days and rehydration for 3 days,and a bZIP transcription factor(ZmbZIP26)was screened from transcriptome data in response to drought and rewatering treatment.Co-expression network analysis revealed that ZmbZIP26 was at the core node of network regulation.The gene contained a 558 bp open reading frame encoding 185 amino acids,which was a hydrophilic protein.Phylogenetic tree and conserved sequence analysis showed that ZmbZIP26 protein had high homology with homologous proteins of sorghum and Miscanthus,and also had the same conserved motifs at the same amino acid positions.Cis-element analysis showed that the upstream 2 000 bp region of the ATG site contained drought response elements,hormone response elements and light response elements.qRT-PCR analysis showed that ZmbZIP26 was a constitutively expressed gene,which was highly expressed in young stems,female panicles and roots.ZmbZIP26 positively responded to drought,high temperature,high salt and nitrogen stress and the process of restoring,which might play an important role in the process of plant resistance.Subcellular localization analysis revealed that ZmbZIP26 was a nuclear protein localized in the nucleus.Protein interaction prediction showed that ZmbZIP26 might interact with zinc finger protein,serine protein,Ca-dependent protein and glutathione transfer protein to construct a regulatory network,which cooperatively regulated maize growth and development and stress response process.

Yield and nitrogen accumulation of maize will decline under soil acidification,but the physiological mechanism is not clear.Field experiment was conducted with four different soil acidity gradients:nautral acid(pH=7,CK),weak acid(pH=6,T1),medium acid(pH=5,T2)and strong acid(pH=4,T3),comparing yield,nitrogen accumulation,grain protein content,nitrogen metabolism-related enzyme activities,gene expression,nitrate nitrogen,ammonium nitrogen,soluble protein,free amino acid content in leaf and stem of maize.The results showed that compared with CK,the yield of T1,T2 and T3 treatments declined by 4.2%,30.7% and 52.3%,respectively.Grain number per spike decreased by 1.8%,28.1% and 42.8%;grain protein content showed a downward trend with T3 treatment significantly reduced by 14.5%.At the big flare stage,with the increase of soil acidity,nitrogen accumulation in leaves showed a downward trend,it was significantly decreased in T2 and T3 treatment by 28.1% and 56.2%,respectively.In stem,the nitrogen accumulation increased firstly and then decreased.Compared with CK,T1 treatment was significantly increased by 33.1%,and T3 treatment significantly decreased by 65.4%.At the big flare stage, the activities of nitrate reductase, glutamate dehydrogenase and glutamate synthase in leaf and stem under T3 treatment were significantly higher than those in CK, while the activities of glutamine synthase in leaf were significantly decreased. The amino acids in stem decreased first and then increased.With the increase of soil acidity,the expressions of ZmGln2 and ZmFd-GOGAT were up-regulated,which promoted the assimilation of {{\mathrm{NH}}_4}^{+} released by photorespiration and {{\mathrm{NH}}_4}^{+} produced by {{\mathrm{NO}}_3}^{-} reduction;the down-regulated expression of ZmGln1.2-ZmGln1.4, ZmNADH-GOGAT2 in leaf and ZmNADH-GOGAT1 in stem decreased the assimilation of {{\mathrm{NH}}_4}^{+} released by catabolism.By up-regulating or down-regulating the expression of relevant genes,maize could promote the production of more free amino acids and soluble proteins during nitrogen metabolism to resist acidification stress,but also reduced the nitrogen accumulation,resulting in lower yield and grain protein content.

To increase crop yields,reduce the application of chemical fertilizers,and improve nutrient utilization efficiency,N-efficient maize cultivars were screened and popularized. An understanding of nitrogen uptake,utilization,and field balance in maize cultivars with contrasting nitrogen efficiency response to N management is essential for efficient breeding and cultivation of maize to produce fodder and bio-energy. To determine the effects of N management on these factors during maize cultivation,a two-year field experiment was conducted in 2015 and 2016 in a subtropical semi-humid climate zone. The results showed that the proportion of N in the stem plus sheath and leaves in ZH311 during VT and R6 was significantly higher than that of XY508. In addition,the N accumulation into grain post-silking(NAG)and contribution of NAG to grain(CNAG)of ZH311 were significantly higher than those of XY508,while the N redistribution rate(NRR)and contribution of NRA to grain yield(CNRA)of ZH311 were significantly lower than those of XY508. The higher proportion of N in the vegetative organs of a N-efficient cultivar,ZH311,led to a significantly higher N accumulation in each stage than that observed for the N-inefficient cultivar XY508. The N accumulation advantage of ZH311 was higher after silking than before silking. The high post-silking N accumulation of ZH311 inhibited the pre-silking N transport that determines the N transport rate and contribution rate to grain of pre-silking N accumulation,which were significantly lower than those of XY508. Meanwhile,the N uptake efficiency,N recovery efficiency,and N partial productivity of ZH311 were significantly higher than those of XY508. Compared with that of XY508,the root system of ZH311 could more effectively absorb and utilize inorganic N in the 40-80 cm soil layer,reduce N deposition,and significantly decrease apparent N losses. The differences in apparent N losses between the two cultivars were mainly elicited post-topdressing. In summary,ZH311 has not only a higher yield per unit area than XY508,but also lower N losses,consequently reducing environmental risks.

The aim of the study was to explore differential expression of genes and metabolites in Zhengdan 958 and Xianyu 335 exposed to high temperature for 7,14 d during grain filling stage and identify the key candidate genes,transcription factors and metabolites,so as to understand molecular mechanism of high temperature tolerance in maize. The ear-leaf samples collected before high temperature treated(CK),7 d high temperature treated,14 d from Zhengdan 958 and Xianyu 335 were used for RNA-sequencing using Illumina HiSeq^TM 2500 high-throughput sequencing technology. Metabolome variations analyzed using liquid-chromatography-mass spectrometry-based metabolomics. A total of 214.81 Gb clean sequence was obtained by transcriptome sequencing. In Zhengdan 958,49 DEGs were detected after 7 days of high temperature treated,of which 24 were up-regulated genes. 306 DEGs were detected after 14 d,130 of which were up-regulated genes. 1 462 DEGs were detected from 7 d samples compared with 14 d samples,of which 647 were up-regulated genes. In Xianyu 335,381 DEGs were detected after 7 days of high temperature treated,of which 164 were up-regulated genes. 299 DEGs were detected after 14 d,226 of which were up-regulated genes. 2 481 DEGs were detected from 7 d treated samples compared with 14 d treated samples,of which 1 275 were up-regulated genes. Comparing Zhengdan 958 samples treated for 7 d with Xianyu 335 samples treated for 7 d,6 646 DEGs were detected,of which 3 253 up-regulated genes. Comparing Zhengdan 958 samples treated for 14 d with Xianyu 335 samples treated for 14 d,5 958 DEGs were detected,of which 3 110 up-regulated genes. A total of 654 metabolites were detected by metabolomics sequencing. In Zhengdan 958,28 DEMs were detected after 7 days of high temperature treated and were annotated into 5 metabolic pathways. 54 DEMs were detected after 14 days,9 of which were up-regulated,and were annotated into 13 metabolic pathways. In Xianyu 335, 98 DEMs were detected after 7 d of high temperature treated,43 of which were up-regulated and were annotated into 24 metabolic pathways. 38 DEMs were detected after 14 d,14 of which were up-regulated,and were annotated into 13 metabolic pathways. Compared Zhengdan 958 with Xianyu 335,144 DEMs were detected after 7 days,81 of which were up-regulated,and were annotated into 36 metabolic pathways.158 DEMs were detected after 14 days,81 of which were up-regulated,and were annotated into 40 metabolic pathways.

Bipolaris sorokiniana is one of the important pathogens of maize root rot.The purpose of the present work was to establish a rapid detection method for B.sorokiniana based on the loop-mediated isothermal amplification(LAMP).Firstly,a set of primers for LAMP assay was designed according to the partial sequence of Brn1 involved in the melanin biosynthetic pathway.Then,the optimal reaction temperature was screened for this primer set,the specificity and sensitivity of LAMP reaction were detected,and the LAMP detection was evaluated by using the maize root rot samples artificially inoculated with B.sorokiniana.The results showed that the primer set designed could amplify the target gene Brn1 at 61—68 ℃,with 66 ℃ was the optimal temperature.In the specific detection,the primer set could specifically detect B.sorokiniana from the genomic DNA of 10 main pathogenic fungi isolated from maize root rot plants.In the sensitivity detection,the minimum detection limit for plasmid DNA carrying Brn1 was 10 copies/μL,and amplification could be achieved in about 25 min at the minimum concentration.And,for the detection of maize root rot samples,B.sorokiniana can be detected in 1 pg/μL of maize root tissue DNA.These results indicated that the LAMP detection method for B.sorokiniana established in this study has robust specificity and high sensitivity.

In order to include the photosynthesis mechanism of summer maize in proper planting mode, in this paper, a split-plot experiment design was used to study the impact of planting densities(93 000, 81 000, 69 000, 57 000 plants/ha), row spacing modes(one plant per spot with equal row, three plants per spot with equal row and three plants per spot with wide and narrow row) and their interaction effects on net photosynthetic rate and its relative traits of a summer maize variety ZD958 at different growth stages(flowering stage, silking stage, earlier filling stage, later filling stage and full ripe stage).The results indicated that the row spacing mode of three plants per spot with wide and narrow row could significantly decrease net photosynthetic rate of ear leaves at flowering stage and full ripe stage.At the planting density of 81 000 plants/ha, the net photosynthetic rate was not associated with row spacing modes.Meanwhile, under the row spacing mode of one plant per spot with equal row, planting density did not significantly affect net photosynthetic rate of ear leaves.It was noteworthy that the carotenoid content was closely associated with planting densities, row spacing modes and their interaction effects.Under the row spacing mode of three plants per spot with equal row, the planting density of 93 000 plants/ha significantly decreased carotenoid content at the first three growth stages, while both the densities of 69 000 under the mode of three plants per spot with wide and narrow row and 57 000 plants/ha under the mode of one plant per spot with equal row could significantly reduce carotenoid content at the full ripe stage.It was also found that the maximum photochemical efficiency of PSⅡ was not influenced by planting densities, row spacing modes and their interaction effects.In general, the planting density of 81 000 plants/ha was not closely associated with row spacing modes, which was similar with the relationships between the row spacing mode of one plant per spot with equal row and planting densities.In these two circumstances, the net photosynthetic rate and its relative traits could maintain relatively higher levels.Our results could also supply experimental evidences for explaining the relationships among cropping patterns, photosynthetic products source and yield pool based on photosynthetic matters and water physiology(pigment content, fluorescence character, photosynthetic rate, and transpiration rate).

In order to explain the genetic basis of tassel length and locate the related QTLs,289 maize inbred lines were used as the experimental material,the correlation between the tassel length of maize and plant height,ear height,tassel stem length were measured and analyzed under natural conditions,and genome association analysis was also applied to initially map the length of tassel. The results showed that tassel length and the three agronomic traits were significantly or extremely significantly correlated,therein,tassel length had the most significant correlation with tassel stem length,and the highest correlation coefficient has reached 0.717.At the same time,a total of 13 marker sites correlated with tassel length were identified and they were located on Bin1.05,Bin7.02,Bin8.03 and Bin10.05. Genome-wide association analysis was used to explore the long locus and candidate genes,which had an important significance to reveal the genetic mechanism of tassel and accelerate the process of maize breeding.

This study to Laiyang in Chao Soil Region long-term positioning straw of wheat-maize rotation as research object,applying nitrogen fertilizer were studied under the condition of straw returning and the single application organic fertilizer on wheat and maize yield and grain quality of influence.At the same level of nitrogen fertilizer,the two crop straw returning to field application of nitrogen fertilizer (WCN) treatment of wheat,corn grain crude fat content compared with a quarter of straw to field nitrogen fertilizer (WN) treatment significantly increased by 5.72% and 9.49%.The proportion of straw was more conducive to improve the crude fat content of grain.WCN processing wheat,corn grain protein content than those of the other two season straw (WC) treatment significantly improved 32.53%,72.44%,showed that the proportion of nitrogen bigger was beneficial to improving the protein content.Single application of organic fertilizer and two season straw returning to field application of nitrogen fertilizer could significantly improve the yield of wheat and maize.Different straw returning treatment on wheat grain lysine,cystine acid,alanine had little effect,the corn grain cystine acid,glutamic acid,glycine has little effect,except for aspartic acid,leucine,valine,lysine lysine,cystine acid,alanine,long-term different straw also fields of other amino acids.To sum up,the application of nitrogen fertilizer on the basis of straw returning to the field can get higher yield and improve grain quality.

In order to study the effects of maize straw returning and nitrogen application on the growth and nutrient absorption of summer maize in wheat-maize rotation system, the experiment was started from 2015 to 2019 and carried out in Renshou County, Sichuan Province.The summer maize variety was Zhenghong No. 6. The experiment was laid out in a split-plot design, with wheat season maize straw returning or not as the main factor and nitrogen level(0, 120, 180 kg/ha) as the sub-plot. After wheat harvest, summer maize was directly planted in each plot, and nitrogen application amounts were 225 kg/ha. The results showed that the soil organic matter content increased by 34.1% after wheat harvest. Similarly, total nitrogen, alkaline hydrolysis nitrogen, available phosphorus and available potassium increased by 6.64%, 7.34%, 16.2%, 14.3%(2-years mean value), respectively. Under the treatment of straw returning, the biomass of the later maize increased by 34.7%(2018), 38.8%(2019), and the yield increased by 65.7%(2018), 30.7%(2019);the biomass of the later maize improved by 29.9%, 36.7% under the treatment of 120, 180 kg/ha, respectively, and the yield increased by 41.5%, 59.4%. By maize straw returning, the uptake of nitrogen, phosphorus and potassium in the above-ground of the later maize increased by 47.2%, 58.8%, 45.0% respectively(2-year mean value). With the increase of nitrogen application rate, the absorption amount of nitrogen, phosphorus and potassium of later maize plants showed an increasing trend. In conclusion, the winter wheat-summer maize rotation planting mode in the southwest hilly region, long-term return of maize straw could improve soil fertility, improve the yield and nutrient absorption of the later maize, which was a green and resource efficient production mode in the southwest hilly region.

In order to investigate the effect of fertilizer reduction combined with organic fertilizer on the yield and quality of silage corn and soil nutrient,in 2019 and 2020,the effects of fertilizer reduction and organic fertilizer on agronomic traits,yield, quality,soil nutrient content and fertilizer utilization rate of silage corn were studied.As a result,the yield of silage corn was significantly affected by different fertilization treatments,and the yield of mixed application of organic fertilizer and slow control fertilizer reached 55 084.75 kg/ha,dry matter production reached 24 192.11 kg/ha.There was no significant difference in yield between slow controlled fertilizer constant and slow controlled fertilizer reduction of 20%,that was,excessive fertilization had no significant effect on yield.The accumulation of N,P and K under T2 treatment was 234.83,173.75,35.72 kg/ha,and significantly higher than other treatments.The maximum nitrogen fertilizer productivity of silage corn under T4 treatment was 166.46 kg/kg,and the maximum nitrogen fertilizer utilization efficiency under T1 treatment was 0.80 kg/kg,which indicated that the mixed application of organic fertilizer and inorganic fertilizer could improve the productivity of silage corn.After T4 treatment,the crude fat content of silage corn was the highest,and the application of organic fertilizer could increase the crude fat content of silage corn,and also increase the content of acid washing fiber.The yield of silage maize was correlated with urease,catalase and available phosphorus content,the correlation coefficients were 0.845,0.798,0.784.The results showed that fertilizer reduction and organic fertilizer application in Southwest China could significantly improve the yield and quality of silage corn,which was beneficial to the protection of farmland ecological environment and the sustainable utilization of soil fertility.

In order to explore the influences of exogenous ABA on cold resistance of maize,we selected two maize materials(cold resistant Qingnong 105 and the cold sensitive agricultural Nonghua 101 as the experimental materials)were used as the experimental materials,after the treatment of low temperature and external application of ABA. The MDA content,relative conductivity,soluble sugar content,protective enzyme activity and hormone content of two maize varieties were determined,and the expression of low temperature stress related genes was compared by fluorescent quantitative PCR. The results showed that the content of MDA and relative conductivity of two maize varieties under low temperature stress were reduced by exogenous ABA treatment,and the content of soluble sugar was increased. The MDA content and conductivity of the cold resistant cultivar Qingnong 105 decreased greatly,while the soluble sugar content increased greatly,Exogenous ABA played a more significant role in the cold resistance of Qingnong 105. By analysis of enzyme activities and hormone levels,exogenous ABA could improve SOD,POD,CAT,APX activities caused by low temperature stress and enhance the ability of active oxygen in order to reduce the accumulation of reactive oxygen species. Exogenous ABA had more obvious effect on Qingnong 105 than Nonghua 101 because Qingnong 105 possessed stronger increase in SOD,POD,CAT,APX activities. We found that exogenous ABA application increased endogenous ABA biosynthesis under low temperature stress,simultaneously reduced the levels of GA₃,ZR,IAA. The effect of low temperature and ABA treatment on cold-resistant cultivar was more obvious. Molecular evidence from RT-PCR showed that exogenous ABA increased the expression level of some genes involved in abiotic stresses under low temperature stress. By comparison of the capacity of these two varieties to low temperature,low temperature stress leads to upregulated Apx1, Fad8, Lip15, Cat3 gene in these two varieties,also Dreb1, Asr1 gene in Qingnong 105,but downregulated Dreb1, Asr1 gene in Nonghua 101. We found that external application of ABA had a significant effect on cold resistant maize varieties. The data could provide some strategies to avoid damages from chilling injury for maize production in China North Area.

To improve the efficiency of high quality wheat breeding program,clarify the composition of HMW-GS and Gliadin in the early generation,296 lines from the wheat maize cross were analyzed useing SDS-PAGE method in this experiment,along with this Gliadin were analyzed useing A-PAGE method.A statistics showed that female parent Heng 09-6324 carried null,7+9,2+12 subunits,and were 1BL/1RS translocation lines with Sec-1 characteristic band.Male parent Shiluan 02-1 carried 1,7+9,5+10 subunits,and were non 1BL/1RS translocation.Six types of HMW-GS all originated from parents were identified from 296 DH lines.The frequency of subunits 5+10 which positively related to bread baking quality was 35.13%.A statistics showed that in the A-PAGE the type of translocation of the DH lines accounted for 54.05%,and the percent of lines with subunits 1 and 5+10,but non Sec-1 translocation were 15.20%,these lines could be used as new germplasm for quality breeding.The paper indicated that that the method of half-seed SDS-PAGE and A-PAGE which could be used to identify and select excellent plants in early generation breeding effectively.