To clarify the regulatory effect of nitrogen(N)fertilizer reduction and postponing on the productivity of wheat-maize double cropping system in Huang-Huai-Hai Plain.The annual N fertilizer experiment of summer maize and winter wheat was established of four N application systems:annual N fertilizer application 400 kg/ha of traditional farmer treatment(F₄₀₀),10% reduction of annual N fertilizer(FN),20% reduction of annual N fertilizer(FH),and 30% reduction of annual N fertilizer(FL)from 2020 to 2023 at Jiyang Experimental Base of the Shandong Academy of Agricultural Sciences in Jinan.The grain yield,aboveground N accumulation characteristics,N use efficiency,and the nitrate residue after harvest in the 0—200 cm soil layer of wheat-maize double cropping system were tested,in order to provide the theoretical basis for further optimization of N fertilizer management in Huang-Huai-Hai Plain.The results indicated that N fertilizer postponing was optimized the grain yield of summer maize and winter wheat under the condition of N reduction,and the averaged across the three years,FL significantly increased by 9.2%—18.1%,13.5%—20.5%,and 11.1%—19.1%,respectively,compared with F₄₀₀ and FN.N fertilizer postponing improved the N accumulation rate,and promoted aboveground N accumulation at wheat-maize different growth stages,and the averaged across the three years,FL significantly increased plant N accumulation by 5.7%—12.3% and 5.0%—12.8% under silking and maturity,respectively,compared with F₄₀₀,FN,and FH,as well as 8.2%—17.2% in grain N accumulation.For winter wheat,FL and FH treatments were significantly higher than F₄₀₀ and FN at jointing,anthesis,and maturity,and the averaged across the three years,FL and FH significantly increased by 23.4%—28.1%,20.7%—26.3%,and 12.6%—20.8%,respectively,compared with F₄₀₀,FN and FH,at the same time the grain N accumulation under FL significantly increased by 16.4%,15.0% and 5.8%,respectively,compared with F₄₀₀ and FN.N fertilizer postponing optimized the N use efficiency of wheat-maize double crop system,the averaged across the three years,FL significantly increased N uptake efficiency by 4.8%—57.7% and 32.0%—72.4% of summer maize and winter wheat,respectively,compared with F₄₀₀,FN,and FH;and FL significantly increased N partial factor productivity by 68.8% and 40.4% in summer maize,respectively,compared with F₄₀₀ and FN,as well as by 38.4%—71.8% in winter wheat compared with F₄₀₀,FN,and FH.At harvest of summer maize and winter wheat,the soil nitrate residue was mainly enrichment in the 0—40 cm soil layer under four N application systems,the averaged across the three years,accounted for 40.0%,38.9%,44.9%,42.5% and 37.3%,36.9%,46.7%,38.3% of the 0—200 cm soil layer,respectively.In addition,the obvious accumulated effects in 0—200 cm soil layer nitrate residue under F₄₀₀ and FN treatments at harvest of summer maize and winter wheat,but there was the relative balance was achieved under FL and FH treatments.In conclusion,a 30% reduction of annual N fertilizer by N fertilizer postponing could optimize plant N accumulation characteristics and realized synergistic improve grain yield and N use efficiency.Therefore,FL treatment was an optimal N application system for realizing the collaborative target of high-yield,high-efficiency,and environment-friendly of wheat-maize double cropping system in Huang-Huai-Hai Plain.

To investigate whether earthworm castings can affect the bacterial diversity of maize soil inside and outside the facility,so as to provide a reference for studying the difference in soil ecological quality between earthworm castings inside and outside the facility at the microbial level.Based on Illumina NovaSeq sequencing platform,16S rRNA sequencing was performed on rhizosphere soil bacteria of maize in different planting modes(different varieties of maize in and outside earthworm manure facilities and different varieties of maize in and outside conventional facilities).A total of 35 627 operational taxonomic units(OTUs)were obtained after quality control,with a total of 1 832 428 valid sequences.The OTU number of soil samples,bacterial community structure,relative abundance,the difference between dominant bacteria genera and groups,and the difference in bacterial diversity analysis were compared under different planting patterns.The OTU number of soil samples was significantly different between earthworm droppings and conventional planting mode.The OTU number of earthworm droppings was higher than that of conventional planting,but the difference was not significant between earthworm droppings and different maize varieties.The dominant microphyla of soil community structure were basically the same,but there was a large difference in the abundance of microphyla between inside and outside the facility and whether or not earthworm castings were applied,and there was little difference between different maize varieties.At the phylum level,the relative abundance of Proteobacteria and Bacteria in and outside conventional planting facilities(class D)was higher than that in and outside vermicomical planting facilities(class E),while the relative abundance of Actinobacteria and Blastomonas in and outside conventional planting facilities(class E)was higher than that in and outside conventional planting facilities(class D).At the generic level,Sphingomonas,Unclassified_Gemmatimonadaceae,Subgroup_10,Unclassified_Bacteria and Unclassified_Vicinamibacteraceae were found to be more abundant in worm castings than in conventional ones.While Unclassified_Microscillaceae,Altererythrobacter,Flavobacterium,Unclassified_Vicinamibacteraceae and Uncultured_gamma_proteobacterium,these five genus had a higher abundance in conventional cultivation than in vermicompost cultivation.The results of diversity analysis showed that the Chao1,Ace,Shannon and Simpson indices of earthworm manure planting(type E)were significantly higher than those of conventional planting(type D).The number and diversity of soil bacteria in earthworm manure planting mode were higher than those in conventional planting mode,and different planting modes significantly affected the composition of soil bacterial community.

In order to determine the effect of different size ear grain characteristics on the mechanical grain crushing rate of corn,Xianyu 1171 and Zhenghong 505 were used as experimental materials to divide the ear into large ear,middle ear and small ear,and determine the agronomic traits,mechanical strength,grain water content and grain crushing rate of corn ear at different harvest periods.The variation of grain water content and mechanical strength of corn with different size ears was studied,and the effect of ear size on the crushing rate of corn with mechanical grain harvesting was analyzed.The results showed that the grain breakage rate of Xianyu 1171 decreased first and then increased slightly,and the grain breakage rate of Zhenghong 505 decreased,and the difference of grain breakage rate between varieties gradually narrowed.The grain breakage rate of spicles was significantly lower than that of middle ear and big ear, and the grain breakage rate of Zhenghong 505 decreased by 16.98 and 20.96 percentage point compared with that of middle ear and big ear,respectively.The grain breakage rate of Xianyu 1171 decreased by 18.63 and 22.43 percentage point compared with that of middle ear and big ear.The grain water content of Zhenghong 505 was significantly higher than that of Xianyu 1711.The grain water content of Xianyu 1171 was mostly mostly significantly higher than that of middle ear and big ear,while that of Zhenghong 505 was lower than that of middle ear and big ear.The endosperm puncture strength of spicule Xianyu 1171 was mostly significantly lower than that of middle panicle and big panicle,but there was no significant difference in crushing strength.There was no significant difference in grain mechanical strength among panicle sizes of Zhenghong 505.Correlation analysis showed that grain breakage rate was significantly of extremely significantly positively correlated with water content,ear length,ear diameter and ear volume,but extremely significantly negatively correlated with grain mechanical strength.Moderate reduction of ear length,ear diameter and ear volume of corn can significantly reduce the crushing rate of corn grain in mechanical grain harvesting.Therefore,it is an effective measure to reduce grain crushing rate by selecting small ear corn varieties or reducing ear size by increasing density and other cultivation measures.

To study the photosynthetic characteristics,fluorescence parameters and yield response to phosphorus in maize,and to clarify the optimal phosphorus application rate for maize under drip irrigation and water fertilization technology.Providing solid theoretical basis and technical support for high-yield and high-efficiency cultivation of maize in Ningxia region.The experiment was carried out at Pingjipu Farm,Yinchuan,Ningxia,from 2019 to 2020,with six phosphorus treatments in the order of 0(P0),60(P1),120(P2),180(P3),240(P4),and 300 kg/ha(P5).Analysis of the changing patterns of photosynthetic and fluorescence parameters of spring maize leaves and their correlation with yield under different phosphorus fertilizer treatments.In two years,during the big bell mouth stage,leaf area index (LAI) was increased by 4.21% to 12.78% and 4.68% to 15.60% for P3 compared to other treatments,respectively.Phosphorus fertilizer at 180 kg/ha was most effective in promoting leaf area index and photosynthetic potential(LAD) of maize.LAD was significantly increased by 14.42% under P3 treatment compared to no phosphorus fertilizer treatment during the full two year period.The photosynthetic characteristics of maize responded differently to the intensity of phosphorus application,and as the intensity of phosphorus application increased,the net photosynthetic rate (Pn) all reached the maximum value after the stamen pumping stage,and at the R1 stage of the 2 years,the Pn was significantly increased by 10.68% under the P3 treatment as compared to the no-phosphorus-fertilizer treatment.The coefficient of determination (R²) was 0.926 5,0.889 9,and 0.832 0,respectively.Phosphorus application increased the maize photosystem Ⅱ composite performance index (PI),which had its maximum peak at the R1 stage in 2 years,and PI increased by 1.12% to 8.50% and 8.47% to 15.40% under the P3 treatment compared with the other treatments,respectively.The maximum yield was obtained at 180 kg/ha of phosphorus application,which was 17.27% higher as compared to no phosphorus treatment.Based on the analysis of the yield fitting equation,it was shown that the maximum corn yield of 13 823.84 kg/ha was reached at 179.34 kg/ha of phosphorus applied.Pearson's correlation analysis showed that appropriate leaf area index significantly affected maize yield in the late stage,and the photosynthetic parameters all had highly significant effects on maize yield completion;principal component analysis showed that the P3 treatment had the highest composite score for the optimization effect on maize yield.Reasonable transportation of phosphorus fertilizer can effectively ensure higher SPAD value,PSⅡ reaction center activity,improve the capture and utilization of light energy in spring maize,and promote photosynthesis,so as to improve the yield and economic benefits of maize.

To evaluate the potential of SpCas9-NG in maize genome editing,the key gene for chlorophyll synthesis,ZmSCD,was selected as the target.The absence of this gene causes seedlings to exhibit albinism,providing a visual assessment of editing efficiency.Based on the PAM sequence recognition rules of SpCas9 (5'-NGG-3') and SpCas9-NG (5'-NG-3'),target sites were designed on the second and third exons of ZmSCD.These target sequences were successfully constructed into SpCas9 and SpCas9-NG knockout vectors,which were then introduced into the maize inbred line KN5585 using Agrobacterium-mediated genetic transformation.The callus tissues were cultured until leaf tissues differentiated,and the albinism rate was recorded to determine the editing efficiency of the different editors.The genomes of albino seedlings were then sequenced.Through three rounds of genetic transformation,SpCas9 produced 76,125 and 28 callus tissues,while SpCas9-NG produced 100,69 and 30 callus tissues.The results showed that the gene editing efficiency of SpCas9 across the three transformations was 14.47%,13.60%,and 10.71%,respectively,while SpCas9-NG editing efficiency was 12.00%,10.14% and 13.33%.Sequencing results of the albino seedlings revealed overlapping peaks near the target sites for both editors.The study demonstrates that SpCas9-NG had comparable editing efficiency to traditional SpCas9 in maize,showing similar gene editing capabilities.In contrast,SpCas9-NG has a broader PAM sequence adaptability,allowing for more flexible target design.This flexibility enables more precise and diverse editing within the maize genome.

Salt-alkali stress has become one of the important factors restricting agricultural production in my country.Exploring the molecular mechanism of salt tolerance of crops has important theoretical and practical value for crop breeding.The purpose of this study is to clone the ZmMPI gene in corn and transform corn plants.First,qRT-PCR was used to analyze the ZmMPI expression changes in plants treated with saline-alkali solutions.Then DNAMAN software was used to perform multiple comparison analysis of the ZmMPI protein sequence.MEGA 7.0 software was used to construct a phylogenetic tree,and a series of software were used to analyze the ZmMPI protein sequence.ZmMPI performed bioinformatics analysis.Finally,molecular cloning technology was used to successfully clone the coding sequence of the ZmMPI gene,construct a plant overexpression vector,and use Agrobacterium-mediated genetic transformation method to transform the corn inbred line B104.The overexpression transgenic plants were transformed at the genome level,transcription level and protein level.Identify and analyze changes in expression levels.The results showed that the expression level of the ZmMPI gene showed an overall trend of first increasing and then decreasing after being subjected to salt-alkali stress;the ZmMPI protein sequence comparison result showed a similarity rate of 64.15%,and the phylogenetic tree showed that ZmMPI had the highest homology with Zea mays subsp.parviglumis ABA34115.1.The protein contained a protein domain Potato_inhibit,which had an α-helix,a random coil and a β-turn.It was relatively hydrophobic and had 10 predicted Potential phosphorylation sites;the identification results of the 49 transformation events obtained showed that the ZmMPI gene in 13 over-expressed transgenic lines could be expressed normally at the genome level,and the ZmMPI gene in 10 over-expressed transgenic lines could be transcribed and translated normally.Finally,10 overexpression transgenic lines capable of normal transcription and translation were obtained,laying the foundation for further exploring the molecular mechanism of ZmMPI gene in response to salt-alkali stress.

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.

The domain of unknown function 668(DUF668)family is a family of plants whose function is unknown.To unveil the function and characteristics of maize DUF668(ZmDUF668)gene family,we identified ZmDUF668 gene family by bioinformatics method.The results showed that there were 19 ZmDUF668 genes in maize,distributing on 8 chromosomes,named ZmDUF668-1—ZmDUF668-19;the most of proteins encoded by ZmDUF668 were alkaline,and most of the family members were localized in the nucleus,cytoplasm and chloroplast.ZmDUF668 family proteins can be divided into two subfamilies according to the multispecies phylogenetic tree.Ten Motifs were identified from 19 members of ZmDUF668,all of which contained Motif 1 and Motif 5.Through the analysis of protein conserved domain,it was found that 14 of the 19 members contained not only DUF668 domain but also DUF3475 domain.Gene structure analysis showed that members of the same subfamilies had similar gene structure.Synteny analysis showed that there were 21 collinear relationships between 13 ZmDUF668 genes and 10 OsDUF668 genes.The analysis of cis-acting elements revealed that the promoters of ZmDUF668 genes widely contained cis-elements that light-response,plant hormones and abiotic stress.The prediction results of protein-protein interaction network(PPI)indicated that only ZmDUF668-10 of the ZmDUF668 family proteins had interaction with other proteins.Analysis of RNA-Seq revealed that the gene expression level of some ZmDUF668 gene family members changed significantly under cold,heat,salt stress and ultraviolet treatment.The response of ZmDUF668 family genes to cold and heat stress was verified by RT-qPCR.Bioinformatics was applied to the analysis of the ZmDUF668 gene family,unveiling the characteristics of the members of the ZmDUF668 gene family,and providing theoretical basis for the subsequent study of the molecular biological function of the ZmDUF668 gene family.

Silk color is an important agronomic trait for determining distinctiveness and uniformity of maize variety.In order to analyze the genetic mechanism of silk coloring characteristics of anthocyanins in maize,a doubled haploid(DH)population with 213 lines derived from green silk inbred line WL134 and purple silk inbred line D7 was used for QTL mapping analysis under the environment of 2022 and 2023,respectively.The results showed that there were significant differences in silk coloring characteristics of anthocyanins among different lines and years,the heritability was 0.864.A total of 9 QTLs were detected in two years.These QTLs with phenotypic variation explained(PVE)ranging from 4.83% to 9.26% were detected on chromosomes 2,3,5,6,8,and 9 of maize.A stable and repeatable site qSC5 located between 19.15 Mb and 19.80 Mb was detected on chromosome 5 in two-year data.The LOD scores of the major QTLs were 4.65 and 5.76 in 2022 and 2023 respectively,with phenotypic variation explained(PVE)of 7.22% and 7.17%.It was a new site for regulating silk coloring characteristics of anthocyanins compared with previous studies in maize.Based on SNP markers on both sides of qSC5,90.91% of the genotypes in extreme purple silk DH lines were CCCC,while only 44.00% of the genotypes in green silk DH lines.This marker was significantly correlated with silk color in maize and might link to key genes regulating silk color characteristics of anthocyanins.

To explore the effects of different farming modes on the growth and development,photosynthesis,leaf structure and yield of maize,and to provide a theoretical basis for optimizing the cultivation measures and creating efficient planting patterns of maize in Hexi oasis irrigation area.Two tillage methods,no-tillage(NT)and conventional tillage(CT),and three planting patterns,wheat-maize intercropping(W/M),winter rapeseed-maize rotation after wheat(W-G→M),and wheat-maize rotation(W-M),were set up in the experiment,with a total of 6 treatments.The results showed that compared with CT,the plant height,stem diameter and leaf area of NT maize increased by 6.83%,4.10% and 3.97%,respectively.The dry matter quality of intercropping maize was higher than that of rotation,but the difference was not significant.The leaf pigments increased first and then decreased with the growth period,which showed that NT chlorophyll a,b and carotenoids were 11.93%,22.41% and 13.43% higher than CT,respectively,and the difference was significant.The net photosynthetic rate(Pn)and intercellular CO₂ concentration(Ci)of NT leaves were 9.17% and 3.81% higher than those of CT.The stomatal conductance(Gs)and transpiration rate(Tr)of CT treatment were 9.95% and 1.48% higher than those of NT.The leaf structure of NT maize was better,the mesophyll cells were more and arranged in order,the vascular bundles were clearly visible,the garland structure was larger,the palisade tissue and sponge tissue were rich,and the leaf thickness of NT was 2.51% thicker than that of CT,and the difference was significant.The yield of NT maize increased by 8.02% compared with CT,and the yield benefit of intercropping was greater than that of rotation(LER>1).This study found that the growth and development,leaf structure and yield of no-tillage maize were better than those of traditional tillage,and wheat intercropping maize could be promoted as the main farming mode in this area.

Auxin response factor(ARF)is a class of transcription factors with B3 domain,which is a direct molecule regulating auxin response and controlling gene expression.A gene,ZmARF10,which encoded ARF protein and actively participated in drought-rehydration stress response,was previously screened in maize by analyzed transcriptome data.To further research the molecular mechanism of ZmARF10 regulating drought resistance of maize,and also provide a new idea for molecular breeding of drought resistance,the gene was firstly analyzed by bioinformatics software.Secondly,Quantitative Real-time polymerase chain reaction(qRT-PCR)was used to detect the expression pattern of ZmARF10 in different tissues,under high temperature,drought,high salt,ABA and restoring treatments,and in different inbred lines.Finally,the function of ZmARF10 was analyzed using CRISPR/Cas9 technology.The results showed that ZmARF10 was located on chromosome 3 of maize,with a total length of 2 127 bp,and encoded 708 amino acids with a typical B3 domain.The upstream 2 kb region of ATG of this gene contained response elements related to methyl jasmonate,auxin,abscisic acid and low temperature.The phylogenetic tree showed that the protein encoded by the ZmARF10 gene was closely related to sorghum.qRT-PCR results showed that ZmARF10 was a constitutive expression gene,and the expression level of ZmARF10 was the highest in mature corn roots of maize.Under high temperature,drought,high salt and ABA treatments,the expression of this gene was significantly up-regulated,and the up-regulation ratio was up to 8.2 times after drought stress.After drought stress,the expression level of ZmARF10 gene was significantly higher in the drought-resistant inbred line Zheng 36 than that in the drought-sensitive inbred line B73.Investigation of Arabidopsis wild type and ARF10-deficient mutants showed that,compared with wild type,the mutant plants showed leaf wilting and even dry death,roots curled,root branch number decreased,and lateral root growth and development were hindered under drought conditions.Determination of physiological and biochemical indexes showed that the relative water content,chlorophyll content and net photosynthetic rate of the deficient mutants were significantly lower than those of the wild-type plants after drought stress,indicating that the drought resistance of Arabidopsis decreased after ARF10 gene was knocked out.

In order to study the correlation between stem traits and the formation of elasticity and density tolerance of maize,and further reveal the mechanism of lodging resistance,6 maize varieties with different lodging resistance were selected as materials,and 3 planting densities of 6.0×10⁴,7.5×10⁴ and 9.0×10⁴ plants/ha were set.The stem pull lodging angle in the field was used as the evaluation index of elasticity,and the morphological characteristics between plants and basal nodes.The internode anatomical structure,material accumulation and mechanical characteristics were analyzed.The results showed that plant height,ear height,basal internode length,thickness,epidermal thickness,crusty tissue thickness,total vascular bundle,sheath area of small vascular bundle,fresh weight per unit length,dry weight per unit length and content of each component,puncture and folding strength had significant effects on the stem pull lodging angle,among which internode diameter(r=0.521^**)and dry weight per unit length(r=0.562^**)had the greatest effects.The greater the planting density,the smaller the internode diameter,the thickness of the hard skin tissue,the total number of vascular bundles,the fresh weight per unit length,the dry weight,the content of each component,the lodging resistance,the worse the elasticity of the stem.There were significant differences in stem traits among different varieties.The elasticity related traits of Lishou 1,Chuangyu 107,Jingnongke 728 and MC278 were better than those of other varieties,and the variation amplitude was smaller with the increase of density,so the elasticity and density tolerance were stronger.Traits such as internode diameter and dry weight per unit length had significant effects on stem pull lodging angle, that was stalk elasticity,and the variation amplitude of these traits after densification determined the density tolerance of stalk.

To clear under the condition of slow release nitrogen fertilizer applying different content of maize development rule of the diurnal change of photosynthetic characteristics and growth,the light response curve was to fit,so as to farming-pastoral zone of spring maize cultivation and nitrogen utilization to provide theoretical basis.This study took Guangde 5 as the research object,and based on the long-term positioning experiment in 2018,the leaves ear position in spinning—tasseling stage of maize were mesured and analyzed under six nitrogen gradient of N 0(N0,CK), 120(N8), 180(N12), 240(N16), 300(N20),360(N24) kg/ha in 2019 and 2020. SPAD value, intercellular carbon dioxide concentration, stomatal conductivity, diurnal variation of net photosynthetic rate, transpiration rate, light response curve and dry matter accumulation rule.The results showed that with the increase of nitrogen fertilizer application, the changes of SPAD value, net photosynthetic rate, transpiration rate and stomatal conduction degree day of maize increased first and then decreased,and N16 treatment was the highest,and intercellular carbon dioxide concentration was the lowest.The changes of net photosynthetic rate,transpiration rate and stomatal conduction degree day showed unimodal curve.The light response curve fitting analysis showed that the maximum net photosynthetic rate of N16 treatment was the highest.In 2019 and 2020,N16 treatments were 37.48%,29.51%,31.85%,18.17%,37.32% and 80.04%,59.73%,50.30%,6.42%,62.51% higher than N0,N8,N12,N20 and N24 treatments,respectively.Dry matter mass accumulation in whole plant and ear were positively correlated with maximum net photosynthetic rate,apparent quantum efficiency and SPAD value.Comprehensive analysis showed that the most suitable nitrogen fertilizer application rate in western Inner Mongolia was 240 kg/ha.

In order to explore the suitable phosphate fertilizer application methods in the Huang-Huai area,this research conducted field experiments to investigate the dry matter accumulation,root morphological indexes,available phosphorus content and phosphatase activity in different soil layers,maize yield and its component factors of four phosphate fertilizer application methods(conventional broadcast (P1),layered application (P2),strip application (P3) and hole application (P4)).The results showed that the ear length and kernel row number of P2 and P4 were significantly increased by 22.57%,16.81% and 15.19%,7.60% compared with P1.The grain number per spike of P2,P3 and P4 were significantly increased by 25.26%,13.86% and 17.00% compared with P1,respectively.Additionally,a decrease of spikes per area was found in P2 (15.30%) compared with P1.The yields of P2 and P4 were significantly increased by 15.20% and 10.79% compared with P1.Among root traits,the root length,root surface area,root volume and root tip number were significantly affected by the phosphorus application method.The root length under P2 and P4 treatments was significantly increased by 30.41% and 33.75% compared with P1.The root surface area of P2 treatment was significantly increased by 23.77% compared with P1.The root surface area of P4 treatment was significantly increased by 29.60% and 21.70% compared with P1 and P3 treatments,respectively.The root volume and root tip number of P2 and P4 treatments were significantly higher than those of P1 and P3.The analysis of soil available phosphorus content showed that the available phosphorus contents of P2 and P4 were significantly higher than that of P1 in the soil layer of 10—20 cm at three-leaf stage of maize.The available phosphorus contents of P2,P3 and P4 in the 0—20 cm soil layer were lower than that of P1,and the available phosphorus content of P4 in the soil layer of 20—30 cm was significantly lower than that of P1 at maturity stage.Correlation analysis showed that there was a significant positive correlation between acid phosphatase activity and soil available phosphorus content in the 10—20 cm soil layer at three-leaf stage of maize.The acid phosphatase activity and soil available phosphorus content in P2 and P4 treatments were higher in this soil layer,which was conducive to the conversion of soil phosphorus into maize absorbable state.In conclusion,compared with the traditional application method,layered phosphorus application and cave phosphorus application can improve the soil phosphorus availability in the early stage of maize,promote the growth and development of roots,and then increase the summer maize yield,so they are more suitable application method for corn phosphorus fertilizer in Huang-Huai area.

This study aims to explore the effects of different concentrations of zearalenone (ZEN) on the growth of bovine mammary alveolar cell-T (MAC-T) and the expression of genes related to milk fat synthesis.Firstly,MAC-T cells were treated with different doses of ZEN for 36 hours,and the number of cells was counted using a hemocytometer.Then,cells were stained and analyzed for apoptosis and necrosis to determine the appropriate dose of ZEN.Next,acommercial detection kit was used to examine the impact of ZEN on reactive oxygen species (ROS) and mitochondria number in MAC-T cells.Finally,using Real-time Quantitative PCR (RT-qPCR) technology,the influence of ZEN on proliferation,apoptosis,oxidative stress,and milk fat synthesis-related gene expression in MAC-T cells was analyzed.The results showed that low doses of ZEN (0.01—1.00 μmol/L) tended to promote MAC-T growth,whereas high doses of ZEN (5.00—10.00 μmol/L) significantly reduced the number of cells,0.10 μmol/L ZEN had no obvious effect on ROS and mitochondria number in MAC-T,but 10.00 μmol/L ZEN notably elevated ROS levels and decreased mitochondria number.RT-qPCR results indicated that 0.10 μmol/L ZEN significantly promoted the expression of proliferation genes (CDK1,CCND2),antioxidant genes (DHODH,GPX4),and anti-apoptotic genes (BCL-2),but also increased the expression of apoptotic genes (CAS-3,BAX).Whereas,10.00 μmol/L ZEN significantly inhibited the expression of proliferation genes (PCNA,CDK1,CCND2),antioxidant genes (DHODH,GPX4,AIFM2),and anti-apoptotic genes (BCL-2),while significantly promoting the expression of apoptotic genes (CAS-3,BAX).Notably,0.10 μmol/L ZEN obviously promoted the expression of milk fat synthesis-related genes (PPARγ,FASN,JAK-2),but 10.00 μmol/L ZEN significantly suppressed these genes.The aforementioned results suggested different effects of ZEN concentrations on MAC-T cells:0.10 μmol/L ZEN could promote MAC-T cell growth and milk fat synthesis-related gene expression while also inducing the expression of apoptotic genes.In contrast,10.00 μmol/L ZEN induces oxidative stress in MAC-T cells,reduces mitochondria number,inhibits the expression of genes associated with proliferation,antioxidant properties,anti-apoptotic properties,and milk fat synthesis,while promoting the expression of apoptotic genes,leading to cell apoptosis.

To investigate the molecular response to drought stress of silks,two treatments with soil moisture content of 80% field holding capacity (CK) and 60% field holding capacity (DS) were set up using Annong 591 and Xianyu 335,and the maize silks were sampled during the rapid increase in silk elongation,and transcriptome sequencing was performed.By comparing the gene expression differences between the drought and control groups of the two varieties,the key pathways and related candidate genes of maize silks in response to drought were clarified.The results showed that the phenylpropane biosynthesis pathway (ko00940) and starch and sucrose metabolism pathway (ko00500) were the key pathways in maize silk response to drought.In the phenylpropane biosynthetic pathway 4CL,CCR,CAD and POD genes were lowly expressed in drought-prone maize silks.Correlation analysis showed that down-regulation of 4CL,CCR,CAD and POD genes was associated with reduced lignin content.Converting enzyme and sucrose synthase genes in the starch and sucrose metabolic pathways were lowly expressed in drought maize silks.Correlation analysis indicated that down-regulation of convertase and sucrose synthase genes was associated with sucrose metabolism.In summary,this study identified key genes and metabolites involved in sucrose and lignin metabolism.The lignin synthesis are associated with drought tolerance in maize silks,and 4CL, CCR,CAD,and POD are the candidate genes for drought tolerance in maize silks.In addition,the starch and sucrose metabolic pathways are associated with silk elongation and drought tolerance of silks,and invertase and sucrose synthase are the main candidate key enzymes.

To explore the physiological response mechanism of maize to different drip irrigation quotas,a 2-year pond planting experiment was conducted under controlled conditions.Using two maize varieties with differences in drought resistance as materials,six treatments were set up:CK1 (Drought resistant variety,500 mm),T1 (Drought resistant variety,350 mm),T2 (Drought resistant variety,200 mm),CK2 (Drought sensitive variety,500 mm),T3 (Drought sensitive variety,350 mm),and T4 (Drought sensitive variety,200 mm) to analyse the photosynthetic,chlorophyll fluorescence,photosynthetic response characteristics,and grain filling characteristics of maize leaves changed in hormone content,starch synthase activity,and yield in grains.The results showed that four photosynthetic parameters,including net photosynthetic rate (Pn),and four chlorophyll fluorescence parameters,including maximum photochemical quantum yield of photosystem Ⅱ (Fv/Fm),decreased with the decrease of drip irrigation quota,while stomatal limitation percentage (Ls) and non-photochemical quenching coefficient (NPQ) increased.The apparent quantum efficiency (AQE) and other 10 photosynthetic response related parameters of maize leaves all decreased with the decrease of drip irrigation quota.The range of differences between light compensation point (LCP) and light saturation point (LSP),CO₂ compensation point (CCP) and CO₂ saturation point (CSP) in CK1,T1,and CK2 treatments was larger than that in other treatments.The grain filling rate reached its peak at 25 d after anthesis,and the T2,and T4 treatments significantly decreased compared to the CK1 and CK2 treatments.The content of cytokinin (CTK) and auxin (IAA) in grains decreased with the decrease of drip irrigation quota,and the content of abscisic acid (ABA) increased.The activities of acid sucrose invertase,sucrose synthase,starch synthase and adenosine diphosphate glucose pyrophosphorylase in grains of T2 and T4 treatments were significantly lower than those of CK1 and CK2 treatments.The maize yield significantly decreased with the decrease of drip irrigation quota,and the T1 treatment only decreased by 3.45% to 4.51% compared to the CK1 treatment.There was no significant difference between T1 treatment and CK1 and CK2 treatment in the above indicators.The leaves of maize treated with T1 treatment still maintained the photosynthetic performance and photosystem Ⅱ structure,enhanced the adaptability of leaves to light and CO₂,increased the content of hormones related to maize grains and the activity of enzymes related to starch synthesis,effectively regulated the growth and development of maize grains and the filling process,and maize yield and its components performed better.

To clarify the impacts of flooding stress on the morphological structure and activities in different types of roots for maize at seedling,two typical maize cultivars Zhengdan 958(ZD958,a tolerant genotype)and Liyu 16(LY16,a susceptible one)were selected,and five flooding durations at three leaf stage were established:0(CK),2,4,6,8 d,to explore the response law involving morphology and root activities of embryonic and adventitious root to excessive moisture.The results showed that after 2 days of flooding,the root length,root surface area,root volume,root tip number and root fork number of primary root,seminal root and adventitious root in maize were significantly higher than those of CK.With the extension of flooding duration,these indexes decreased obviously,but the average root diameter displayed an outstanding enhancement.Compared with CK,the morphological indexes of emerging adventitious root under flooding performed better,and among them,the root length and root tip number suffered the most from flooding.The total number,the layer number and the angle of adventitious root increased after flooding.With the elongation of flooding duration,except dry weight at the first layer of adventitious root,the primary root,seminal root and secondary layer of adventitious root of ZD958 increased first and then decreased,but those of LY16 decreased from the start.The root-shoot ratio rose from 2 days to 6 days,and then declined after that.The root activities of primary root and seminal root were significantly reduced under flooding,however,the function of adventitious root could be maintained for 4—6 days.It is concluded that the negative effects of flooding on different root types indicated primary root>seminal root>adventitious root,and response features were different from both varieties.In addition,the adventitious root activity and root-shoot ratio of flooding resistant variety begin to decrease after 8 days of flooding.

This research studied the effects of different phosphorus and potassium fertilization methods on maize growth,nutrient uptake and utilization.It was determined suitable fertigation timings and frequencies of phosphorus and potassium fertilizer,and to provide a theoretical basis for drip fertilization technology of maize with phosphorus and potassium in semi-arid areas of northeast China.A field experiment was conducted in 2018—2019,with Xiangyu 998 as a test material,six treatments were set up,P0 (No phosphorus fertilizer),K0 (No potassium fertilizer),P1(100% basal application of P fertilizer,50% basal application of K fertilizer,the other 50% fertigation three times),K1(100% basal application of K fertilizer,50% basal application of P fertilizer,the other 50% fertigation four times),P1K1(100% basal application of P and K fertilizer),and P4K3(50% basal application of P and K fertilizer,the other 50% P fertigation four times and the other 50% K fertigation three times).The results showed that compared with the P1 treatment,the P4K3 treatment increased maize yield by 4.2%,dry matter accumulation at maturity by 6.8% (P<0.05),post silking P accumulation by 33.3% (P<0.05),and significantly improved the P fertilizer recovery efficiency and agronomic efficiency by 21.6 percentage points and 28.5%,respectively.Compared with the K1 treatment,the P4K3 treatment increased maize yield by 3.5%,dry matter accumulation at maturity by 5.1%,and significantly improved the K fertilizer recovery efficiency and agronomic efficiency by 14.9 percentage points and 53.5%,respectively;compared with the single application of phosphorus and potassium treatment,maize yield was increased by 5.0%,the uptake of phosphorus after silking was increased by 26.3%,and P fertilizer recovery efficiency and P agronomic efficiency were increased by 19.5 percentage points and 32.6%,respectively;K fertilizer recovery efficiency and agronomic efficiency increased by 15.2 percentage points and 95.5%,respectively.Fractional fertigation of phosphorus and potassium fertilizer could not only be beneficial to improve yield of maize,but also promote post-silking nutrient uptake and improve nutrient utilization under drip irrigation conditions.Comprehensive consideration,P4K3 treatment is a more suitable drip fertigation technique for field production.

In order to clarify the impact of irrigation amount on maize production,using Zhengdan 958 as the main material and the local average reference crop water demand(ET0)was used as the basis of irrigation volume,a study was conducted under rain-protection shed in 2020 and 2021,which included eight irrigation treatments:T1,T2,T3,T4,T5,T6,T7 and T8 representing 60% ET0,80% ET0,100% ET0,120% ET0,140% ET0,160% ET0,180% ET0 and 200% ET0,respectively.The study aimed at analysing the effects of irrigation on yield and its components and plant physicochemical properties.The results indicated that the yield and its components,ear length,grain dry matter distribution ratio,free water content,plant height,ear position height,ear height coefficient,photosynthetic potential and seed setting rate of maize showed an increasing trend when irrigation was added.Specifically, the yield and grain number per ear increased significantly while the material distribution ratio decreased in leaf and corn cob.There was a small change rate of chlorophyll and water potential of maize leaves,no significant difference in plant height and ear position height among treatments and stable ear height coefficient at VT and R6 stages under high water treatment(T5—T8).Comparing with T3,a decrease of 20% and 40% in irrigation volume could cause a significant decrease in yield,but the lower yield increase rate appeared when irrigation volume had the same increase rate as the decrease rate. The seed setting rate also showed the same variation under the same condition. However,the water supply efficiency decreased with the increase of irrigation volume and declined more than 20% when the irrigation volume exceeded T6.Correlation analysis showed that correlation between maize yield and leaf chlorophyll content,water potential at anthesis and water content was not significant,but there was a significant or extremely significant correlation with other factors.Therefore,maize yield could be raised by improving ear traits,grain dry matter distribution ratio and physical and chemical properties of plant development through irrigation,an increased irrigation amount by 40%—60% on the basis of the average water demand should be suggested for maximizing the yield and efficiency during the growth period in the region.

In order to reveal the influence mechanism of sowing date adjustment on crop yield formation, a field experiment was conducted to adjust the sowing date of the same variety of summer maize from 2019 to 2021 at Hebei Gucheng Agricultural Meteorology National Observation and Research Station in Northern north China, which was set up in four sowing date, as 10 d early sowing, 10 d late sowing, 20 d late sowing and control. By monitoring the growth period changes, plant dry matter accumulation, leaf photosynthetic characteristics and grain filling characteristics, and sampling at maturity to determine the yield components, the results showed that:the sowing date of summer maize was appropriate to be advanced,the seedling stage,ear stage and the whole growth period were extended,especially,the duration of effective filling was extended with the advance of sowing date.The effective grain filling duration days were extended by 4.7 days for every 10 days ahead of the sowing date.The average filling rate of winter wheat was 4.04% higher on the sowing date was advanced by 10 days, compared with the sowing date was deferred by 10 or 20 days and the control.Grain filling accumulation increased,and 100-grain weight increased by 5.459 g.The main yield components of summer maize,such as grain number per ear,grain weight per ear and 100-grain weight showed significant differences during sowing,and increased with the sowing date.The theoretical yield increased by 1 395.4 kg/ha with 10 days ahead of the sowing date during the experimental period from June 8 to July 8.The average net photosynthetic rate(Pn)of leaves in the critical development period of summer maize increased by 0.764 μmol/(m²·s)with every 10 days ahead of sowing date,and the average Pn of sowing date 10 days earlier was increased by 7.31% compared with the control and late sowing 10 and 20 days.With the increase of photosynthetic rate,dry matter production,accumulation and transfer to grain were increased,and the grain weight per ear and 100-grain weight increased by an average of 24.01% and 18.00%,respectively,compared to the control and late sowing 10 and 20 days.Advancing sowing date resulted in low plant height,strong stems,lodging resistance,large individual green leaf area,high leaf area index(LAI),and high leaf photosynthesis ability,above-ground dry matter allocation rate at maturity stage every 10 days in advance of sowing date:grain weight improved by 2.26%,the source—pool distribution of dry matter between plant vegetative organ and ear changed,ear weight per ear,100-grain weight and grain yield increased.The research showed that the double cropping area of winter wheat—summer maize in north China could effectively improve the yield per unit area by making full use of the heat resources increased by climate warming,reasonably allocating stubble,sowing summer maize early at the appropriate time,and extending the development period and grain filling time.

To explore the influence of straw returning years to the field after deep turning back on soil bacterial community in continuous cropping corn fields in the West Liaohe Plain,and provide theoretical guidance for continuous straw returning to improve soil fertility.This study takes corn straw leaving the field as a control (CK),based on the high-throughput sequencing technology of bacterial 16S rDNA V3-V4 region,combined with bioinformatics,we analyzed the characteristics of organic matter,nitrogen nutrients content,soil bacterial community structure and diversity changes in 0-20 cm and 20-40 cm soil layers of corn fields with continuous straw returning for 2(SR2),5(SR5) and 10 a (SR10).The results showed that SR2 had no significant difference with CK in soil organic matter and nitrogen nutrients content,while SR5 and SR10 significantly increased soil organic matter and nitrogen nutrient content;under different straw returning years,soil bacterial diversity was different and each had its own unique OTU,among which SR10 OTU had the largest number;alpha diversity index showed that the relative abundance and diversity of soil bacterial community were not significantly different between SR2 and CK,SR5 and SR10 increased significantly,and SR10 and CK had the largest difference;a total of 51 bacterial groups were obtained at the phyla level,including Actinobacteriota,Proteobacteria,Acidobacteriota,Crenarchaeota and Chloroflexi,whose relative abundance was more than 5%.The relative abundance of Proteobacteria,Acidobacteriota and Chloroflexi increased with the increase of returning years.RDA clustering analysis showed that the soil bacterial community structure of 0-20 cm soil layer SR2 was similar to CK,SR5 was more similar to SR10,20-40 cm soil layer,different straw returning years,treatments were different from CK,SR2 and SR5 were similar,SR10 had significant differences in community structure compared to SR5 and SR2.The contents of soil {\mathrm{NO}}_3^{-}-N, {\mathrm{NH}}_4^{+}-N,OM,and TN all had effects on bacterial flora,and they were soil {\mathrm{NO}}_3^{-}-N> {\mathrm{NH}}_4^{+}-N>OM>TN.The contents of soil organic matter and nitrogen nutrient had no significant difference between continuous straw returning for 2 a and CK,while continuous straw returning for 5 and 10 a were significantly increased.In summary,the microbial diversity and richness of bacteria showed minimal changes in the soil layers of 0-20 cm and 20-40 cm after continuous straws returning for 2 a.After continuous straws returning for 5 and 10 a,both soil layers significantly increased;the bacterial community structure continuous straw returning for 2 a was similar to CK in the 0-20 cm soil layer,while the bacterial community structure continuous straw returning for 2,5,10 a were changed in the 20-40 cm soil layer.

Basic leucine zipper(bZIP)transcription factor protein is a kind of transcription factor with conservative structure and function in animals,plants and microorganisms.In order to clarify the function and mechanism of bZIP transcription factor in plant pathogenic fungi,and further determine its relationship with the growth,development and pathogenicity of the pathogen,the StbZIP9 gene was cloned from Setosphaeria turcica 01-23(GenBank No.XM _ 008032179.1).StbZIP9 is a member of the bZIP transcription factor family.The analysis of the gene structure and protein characteristics showed that the DNA sequence was 788 bp in length,with an open reading frame of 726 bp,encoding 241 amino acids.The encoded protein contained a highly conserved homologous domain BRLZ in fungi.The RNA-seq data of the gene during the growth and development of the pathogen and the process of infecting the host were analyzed.It was found that the expression level of StbZIP9 was 2 to 4 times higher than that in the appressorium and germ tube period compared with the mycelium period.After 24,72 h of infection of maize leaves,the gene expression increased from scratch and continued to increase,indicating that StbZIP9 was associated with appressorium development and germ tube formation and played an important role in the process of pathogen infecting host cells.Further,bioinformatics techniques were used to predict its binding conserved motifs and regulatory target genes.The binding motif was NNTWACGTNN,including the bZIP transcription factor recognition core sequence ACGT,and the downstream target genes of StbZIP9 were predicted according to the sequence.Combined with the expression pattern analysis using the RNA-seq data,four downstream target genes(protein IDs in the JGI database were :132893,163024,162798,40466)were obtained,and the functional annotation table was obtained.The functional annotation revealed its involvement in many biological processes, such as polymerization and transport of cell wall components, host infection, and spore dormancy. It will provide the basis for further elucidation of the molecular mechanism involved in the regulation of pathogen infection.

12-oxo-phytodienoic(OPR) acid reductase is a flavin mononucleotide-dependent oxidoreductase,a key enzyme for the synthesis of jasmonic acid,which is important for plant growth, development and defence regulation.In order to study the disease resistance effect of OPR gene in maize, bioinformatics methods were used to identify OPR family members in 31 different maize inbred lines and the expression pattern after infestation by S. turcica was analyzed.The results showed that eight OPR genes were identified in maize line B73 and they were unevenly distributed on seven chromosomes.In addition,these expressed proteins of OPR genes were rich in acidic amino acids.Further analysis revealed that the maize OPR family contained only one structural domain,Oxidored_FMN,and all OPR members contained 10 protein conserved motifs identified.Phylogenetic relationship analysis of OPR family members from maize,wheat,rice and Arabidopsis using MEGA software revealed significant differences in the evolutionary relationships of OPR gene families in these plants.The OPR proteins of maize and those of rice were the closest in evolution.Homology analysis using OrthoFinder software revealed that the maize OPR gene family was highly conserved,with all OPR genes being core genes,but with slightly different functions.According to the previous RNA-seq data of Hebei key Laboratory of Plant Physiology and Molecular Pathology,we analyzed the expression pattern of OPR genes of maize B73 in response to S.turcica infection and verified the gene expression pattern of OPR genes through qRT-PCR.It was found that there were three different expression patterns in the process of S.turcica infection.This study systematically identified the maize pan-genomic OPR family genes and their expression patterns in response to S.turcica infection.

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.

Maize grain development stage is very sensitive to high temperature stress,which seriously affects the yield and quality of maize.To study the difference of gene expression in grain and analyze the gene molecular mechanism of different high-temperature tolerant maize inbred lines in response to high-temperature stress,RNA-Seq technology was used to analysis the differentially expressed genes(DEGs)of XN202(heat tolerant)and CT110(heat susceptible)in maize grains 15 days after pollination under normal and high temperature stress.Compared with the control,XN202 and CT110 detected 1 517 and 1 012 DEGs,respectively,with 142 common DEGs,including 7 transcription factors.There were significant differences in grain response to high temperature stress among different heat tolerant inbred lines.DNA replication,nucleosome,minichromosome maintenance complex,alpha DNA polymerase:primase complex,nutrient reservoir activity,alanine,aspartate and glutamate metabolism were involved in response to high temperature stress through gene ontology(GO)function annotation and kyoto encyclopedia of genes and genomes(KEGG)signal pathway enrichment analysis.According to bioinformatics analysis,a total of 374 DEGs were located in the reported QTL interval of heat tolerance related traits in maize,and 42 DEGs were putative heat tolerance candidate genes.In summary,maize grains could form complex cellular protection and defense system under high temperature stress,and DEGs related to high temperature tolerance,such as AP2/ERF,MYB,bHLH,NAC,HSF and HSP,might play an important role in the molecular regulatory network.

The glutasidyl thiotransferase gene(GST)can be involved in the process of plants responding to abiotic stresses.In order to understand the ability of ZmGST in response to salt and drought stress in maize,the ZmGST gene was obtained by RT-PCR cloning using the inbred line CA66 of maize as the material,and the gene was bioinformatically analyzed,and the relative expression of the gene in different tissues of maize and simulated drought and salt stress was analyzed by Real-time fluorescence,and the prokaryotic expression vector was constructed and treated with drought and salt.The results showed that the CDS sequence of ZmGST gene was 384 bp in length and encoded 127 amino acids,and the bioinformatics analysis showed that the gene belonged to the Tau family,was a hydrophilic unstable protein,did not have a transmembrane structure,had 12 phosphorylation modification sites,found no signal peptide,was a non-secreted protein,and subcellular localization predicted that ZmGST was located in the nucleus and cytoplasm.The homologous sequence results showed that ZmGST was the closest related to Sorghum bicolor,and had the highest similarity with ZmGSTU14 gene.The promoter analysis results were found to contain TC-rich repeats and other elements,which are involved in defense and stress response.Real-time fluorescence quantitative results showed that the expression of ZmGST gene was the highest in maize roots and was upregulated by salt stress,which reached the highest level after 24 h of treatment.The results of salt and drought stress at the prokaryotic level showed that the recombinant plasmid pET28a-ZmGST could grow normally in medium with different salt concentrations,and the simulated drought was inhibited.It is speculated that ZmGST gene plays an important role in maize response to salt stress.

In order to investigate the effects of nitrogen application rates on the accumulation and distribution characteristics of dry matter and nitrogen,yield and components of maize in the key growth period under different ecological conditions in Inner Mongolia,experiments were carried out in three ecological zones,Tumed Right Banner of Baotou City,Harqin Banner of Songshan District of Chifeng City and Wuyuan County of Bayannur City of Inner Mongolia in 2021.Using maize varieties Xianyu 335,Zhengdan 958 and Jingke 968 as experimental materials,the effects of nitrogen application rate on dry matter and nitrogen accumulation,distribution,transport and yield formation in different organs of maize were studied.The results showed that the interaction between ecological zone and nitrogen fertilizer had a extremely significant effects on dry matter accumulation and distribution,nitrogen accumulation and distribution,yield and its component factors.The proportion of dry matter in various organs of maize varieties in different ecological regions was different,in order of grain>stalk>cob+bract>leaf blade.The difference was mainly manifested in the silking maturity stage. At N2 level,Xianyu 335 had higher dry matter accumulation before flowering and Zhengdan 958 had higher dry matter accumulation after flowering.At the N1 level,the stalk transfer volume,stalk transfer rate and stalk contribution rate of Jingke 968 showed good performance.The nitrogen accumulation of maize varieties with different nitrogen efficiency showed an increasing trend with the advance of growth period.The nitrogen distribution in all organs at maturity stage was grain>leaf blade > cob + bract > stalk.The maize yield in different ecological regions was Harqin Banner>Wuyuan County>Tumed Right Banner.Under the N0 level of Tumed Right Banner,the yield was Xianyu 335>Jingke 968>Zhengdan 958;at the N1 and N2 levels,the yield performance was Zhengdan 958>Jingke 968> Xianyu 335.At the different nitrogen levels in Wuyuan County and Harqin Banner,the yields were Zhengdan 958>Jingke 968>Xianyu 335,and the differences between varieties were significant(P<0.05).In conclusion,the response of nitrogen fertilizer level to Xianyu 335 dry matter accumulation was better in Wuyuan County and Tumed Right Banner.And the response of Jingke 968 and Zhengdan 958 to dry matter accumulation was better in Harqin Banner.Compared with Jingke 968,Xianyu 335 and Zhengdan 958 had better utilization of nitrogen fertilizer at the later growth stage.

To determine the effects of different nitrogen levels on soil nutrient characteristics and on the differences in nitrogen,phosphorus,and potassium uptake and utilization of summer maize,a field experiment had been conducted at four nitrogen rates(N0:No nitrogen application;N1:90 kg/ha;N2:195 kg/ha;N3:300 kg/ha)following nitrogen application of 240 kg/ha on preceding winter wheat.The experimental material Cangyu 76 was used to research the effects of nitrogen application rate on different characters of growth indicators and their correlation.The results showed that the dry matter weight of stem,leaf and corn crobs increased with the increase of nitrogen application ranged in 0-195 kg/ha.Soil nitrate N content in 0-20 cm and 20-40 cm soil layers increased significantly with increasing N application rate;but the content of available P and available K in the same soil layer had no significant change.There were significant differences in nitrogen concentration and nitrogen accumulation in stems,leaves,corn cobs and grains under different nitrogen application rates,in which nitrogen accumulation in seeds accounted for 59.4%-63.5% of total nitrogen accumulation in above-ground parts of plants.The P and K contents in stems,leaves,corn crobs and grains had little change under nitrogen application rate,but was positively regulated by dry matter weight.When N input exceeded 195 kg/ha,nitrogen agronomic efficiency was decreased significantly.When the nitrogen rate was higher than 189 kg/ha,grain yield would be not increased,which was evaluated by Linear plus platform model that simulate the relationship between yield and nitrogen application rate.Therefore,combined with experimental and model simulation results,the optimal nitrogen input was controlled within the range of 189-195 kg/ha,which could realize both economic benefits and agroecological benefits.

In order to explore the effects of different planting densities and potassium(K)application rates on dry matter accumulation and translocation,yield and K use efficiency of maize in the typical black soil region of Northeast China,the two-year continuous located experiment was studied the effects of different planting densities(D1:5.5×10⁴ plants/ha,D2:7.0×10⁴ plants/ha and D3:8.5×10⁴ plants/ha)and K application rates(K0,K40,K80,K120 and K160)on dry matter accumulation and translocation,K use efficiency and yield of maize in Gongzhuling City of Jilin Province.The results showed that there was a significant or extremely significant interaction between planting density and K application rate on dry matter accumulation of maize.The maximum and average accumulation rates of dry matter in D2K120 treatment were at the highest values,and the translocation amount and contribution rate of dry matter remained at higher levels.K recovery efficiency(REK),agronomic efficiency(AEK)and partial factor productivity(PFPK)at the same planting densities decreased with increasing K application rate,and the values reached the highest in D2 under the same amount of K application.Under the same K application rate,the maize yield in D2 was at the highest value.The average yields in two years under D2 were increased by 6.9%,3.0% than D1 and D3,respectively.At the same density,maize yield was significantly improved due to K fertilizer application.Among them,the yield increasing was no longer significant exceeding 80 kg/ha of K application rates under D1,and it was no longer significant exceeding 120 kg/ha of K application rates under D2 and D3.According to fitting a linear-plateau model,the appropriate ranges of K application rates were 72-80 kg/ha,104-115 kg/ha,105-116 kg/ha under D1,D2 and D3,respectively.Under the condition that K application rate in D2 was increased by 44.5% than that in D1 and was equal to that in D3,the maize yield in D2 was increased by 9.8%,3.2%,and REK was increased by 4.1,4.9 percentage points than D1 and D3,respectively.In conclusion,the planting density of 70 000 plants/ha and K application rate of 104-115 kg/ha are appropriate in the typical black soil region of Northeast China.

It aimed to research the variation of mineral elements in the maize grain under the nitrogen(N)and zinc(Zn)fertilization,in order to provide scientific references for N and Zn application in the maize production.In the field plot experiment,two varieties including ZD958 and GSY66 were fertilized with three N rates(90,180 and 225 kg/ha)and four Zn treatments(no Zn,spraying Zn of 1∶1 at seedling stage and jointing stage,spraying Zn of 1∶1 at jointing stage and flare opening stage and spraying Zn at flare opening stage),to analyze the effects of N and Zn fertilization on the maize grain yield and mineral elements concentration and accumulation.The results showed that grain yield was significantly decreased,while Ca,Cu,Fe and Zn concentration as well as Cu and Fe accumulation were significantly increased when the N rate was more than 180 kg/ha.N and P,K,Mg concentration achieved the highest and lowerest values respectively under the 180 kg/ha N treatment.Spraying Zn of 1∶1 at jointing stage and flare opening stage and at flare opening stage only could significantly improve the yield,N and Zn concentration and N,Mg,Zn,B and Na accumulation,but decrease the P,K,Ca,B and Na concentration.Relative to GSY66,the grain yield of ZD958 was significantly increased by 19.3%,and K and Fe concentration and K,Ca,B and Na accumulation were also significantly increased.Grain yield showed extremely significantly negative correlation ship with most mineral element concentration.The positive correlationships among Ca,Mg,Cu,Mn,Fe,Zn and B were significant or extremely significant,expect for Ca and Mg,Zn.The linear regression relationships between grain Zn concentration and N,Mg concentration were significant or extremely significant.To sum up,applying 180 kg/ha N and spraying 4.5 kg/ha Zn of 1∶1 at jointing stage and flare opening stage could increase maize grain yield,N and Zn concentration and mineral elements accumulation,synchronously achieve the high yield and mineral nutrition,and are recommended to promote in maize production.

In the early stage, the dwarf dwarf-12 was successfully selected by distant hybridization of dwarf sorghum and local maize.After previous studies, the dwarf gene may be controlled by br2.Since there were no adverse traits, in order to utilize and discover excellent dwarf inbred lines, and then crossed dwarf-12 with local white maize, and selected the excellent dwarf inbred line d8227. The dwarf maize material d8227 obtained by predecessors was combined with maize of different heights, and it was identified that it has good combining ability. In order to increase the germplasm resources of dwarf maize and improve the yield of maize, in-depth research was carried out.d8227 and dwarf-12 were used as research materials to compare the differences in main agronomic traits between dwarf parents and progeny to observe the differences in stem cytology;d8227 and four inbred lines with different backgrounds were used for genetic mating design to analyze dwarf culm.Inheritance mode of genes; construct a targeting population, perform high-throughput sequencing with BSA method, conduct preliminary mapping of dwarf genes, and perform allelic identification of dwarf materials with known positioning intervals to clarify target genes and known genes relationship. The results showed that the plant height of d8227 increased by 9.35%, the ear position increased by 31.50%, the leaves of d8227 decreased, and the length of stem nodes increased.dwarf-12 increased by 52.21%, 5.26%, 23.76%, 6.93%, 12.02%; using the paraffin section method, observe the characteristics of transverse and longitudinal cells on the upper, ear and lower ear of d8227 and dwarf-12 with a microscope, and d8227 was longitudinally sectioned.The cells were loosely arranged and the cells were obviously elongated;the dwarf-12 cells were arranged regularly and compactly.After measuring the cell area, ear and lower ear cell area of the d8227 were significantly increased than that of the dwarf-12, which was mainly caused by the elongation of the d8227 cells. Through genetic analysis, the dwarf stalk gene was a single recessive gene, and the gene was preliminarily located.The dwarf stalk gene were located at 190-215 Mb of chromosome 1.The dwarf maize that had been located in the interval was selected for allelic identification.The two-year planting results showed that d8227 and 123d, Na360 were not alleles, but may be alleles with 125d and 123d, which needed follow-up fine mapping and in-depth research. On the whole, d8227 is a medium dwarf material with excellent characters and has breeding potential, but further studies such as fine positioning are needed to judge its utilization value.

In order to reduce the labor costs and guarantee the seed purity, male sterility gene was applied to sweet corn hybrid seed production. We used male sterility 2020 (ms2020), a spontaneous male sterility mutant derived from sweet corn inbred line K78, as the experimental material to construct F₁ and corresponding F₂ populations of ms2020 and sweet corn inbred line M08. We performed phenotypic identification, genetic analysis, and gene mapping for ms2020 mutant. Phenotypic identification showed that the F₁ population was fertile, and the F₂ population was partially sterile. The sterile plants could be tasseled normally, but the anthers were not exposed, no pollen shed, anthers small, and pale yellow. Employing 1% I₂-KI staining showed that the anthers of sterile plants contained abortive pollen grains that could not stain normally. The results of genetic analysis showed that the ratio of fertile normal plants to sterile plants was 3∶1, indicating that ms2020 male sterile mutant was a recessive mutant controlled by a single gene. The target gene was initially located on the short arm of chromosome 7 by the BSA method. Subsequently, 20 pairs of SSR markers in the initial interval were used to locate the sterile gene, and gene was finely located between markers S1 and W10, with a physical distance of 11.30 kb. Two genes, Zm00001d018802 and Zm00001d018803 were included in this region. Based on the functional analysis of candidate genes, it is speculated that Zm00001d018802 (ZmMs22/ZmMSCA1) encoding gludodoxin, which has been reported as a male sterility gene in maize, may be the key candidate gene for ms2020.The abortion characteristics and genetic regularity of ms2020 male sterility mutant were identified, which provided the material for male sterility hybridization seed production of sweet corn. The key candidate gene of the mutant were located, which laid a foundation for further analysis of its molecular mechanism.

In view of the problems of excessive input of nitrogen(N)fertilizer,serious nitrogen loss and soil N accumulation,and hard to popularize controlled-release urea(CRU)because of its high cost,this research,based on the field experiment including six crop growing seasons over three years,explored the application effect of combined CRU with urea under the condition of reduced N rate in winter wheat-summer maize rotation and aimed for optimizing the N application rate under applying the optimized blending application ratio of CRU and urea,so as to provide the technical references for reducing chemical N fertilizer input,increasing its use efficiency and generalizing CRU.The experimental design consisted of six treatments:CK(No N application),FH(urea with 270-240 kg/ha N application on winter wheat and summer maize respectively;50% of the total N applied once and 50% dressing).For N1,N2,N3 and N4 treatments, mixture of CRU and urea(controlled release nitrogen accounting for 40% of the total nitrogen content) was applied once before planting at 243,216,189 and 162 kg/ha respectively for winter wheat,and was applied at 216, 192, 168, and 144 kg/ha with controlled release nitrogen accounting for 30% respectively for summer maize.The results showed that:compared with FH,only N1 increased the yield and net profit of winter wheat and summer maize for three consecutive years.For winter wheat,N1 increased significantly the yield by 4.0%,5.4% in 2017-2018 and 2019-2020,respectively,and still increased the yield by 1.6% even in 2018-2019 that the yields of other treatments were decreased.N1 also increased significantly summer maize's yield by 10.9%.In addition,after harvesting winter wheat and summer maize per year,amount of accumulation of inorganic N in 0-100 cm and 60-100 cm soil layer of N1 was significantly lower than that of FH, while the cumulative N use efficiency of N1 after 6 growing seasons of crop was increased by 11.3 percentage point.These results demonstrated that a mixture of CRU and urea (at a ratio of controlled release nitrogen accounting for 40% and 30% of the total nitrogen content for wheat and maize respectively)with a 10% reduction in N application rate compared to FH could be more beneficial to increase crop yield and nitrogen use efficiency, and reduce leaching of soil inorganic nitrogen in wheat-maize rotation system.

Grain specific promoter with high transcription activity can regulate the specific and high-level expression of target genes in plant grains.In order to explore specific promoters of maize grain,the dominant expression gene GRMZM2G006585 was screened from the published data of maize expression profile microarray.The DNA sequence about 2 000 bp upstream of its coding region was cloned and named PZm2G006585.By using the online websites New PLACE and PlantCARE to analyze its promoter elements,we found that it contained multiple grain specific related elements such as E-box and P-box.It was preliminarily considered that the upstream sequence of the cloned coding region was a grain specific promoter from maize.In order to verify its function,the expression vector of GUS gene was constructed and transformed into plants.GUS histochemical staining results of transgenic rice showed that the expression pattern of exogenous genes driven by the promoter was grain specific and embryo dominant.The results of GUS activity detection in T₃ seeds of transgenic Arabidopsis thaliana single copy line showed that the GUS activity driven by PZm2G006585 was 909.52 nmol/(min·mg).The discovery and functional verification of the grain-specific promoter PZm2G006585 can provide candidate promoter resource for specific expression of target genes in maize,rice and other monocotyledons.

To further explore the molecular mechanism of pericarp thickness development in sweet corn, pericarp from sweet corn inbred lines M03 and M08 were used for transcriptome sequencing,these materials provided by the sweet corn breeding laboratory of South China Agricultural University.RNA-sequencing material were sampled at 15,19 and 23 days after pollination.Genes’ differentially expressed analysis combined with weighted gene co-expression network(WGCNA)analysis were used to identify the co-expressed gene modules related to pericarp thickness at the milk stage of sweet corn,and the hub genes were also identified.Quantitative real time-PCR(qRT-PCR)was used to validate the expression level of the hub genes.Here,a total of 4 748 differentially expressed genes(DEGs)were identified by comparing different development stages and different samples.Gene annotation analysis revealed that these DEGs were mainly enriched in carbohydrate metabolic processes,plant-pathogen interactions,and plant MAPK signaling pathways.Co-expression analysis identified 18 modules,in which four modules(Turquois,Yellow,Magenta and Pink)were significantly associated with pericarp thickness.GO and KEGG functional enrichment analysis were performed based on these four specific modules,which could be enriched in alanine aspartate and glutamate metabolism,MAPK signaling pathway-plant and cysteine and methionine metabolism.The top 20 hub genes were screed by calculating the gene connectivity in the corresponding net-works,13 hub genes including MYB transcription factor,cell cycle protein(CYC15),β-amylase,apoptosis regulatory gene(BCL-2),etc.were finally screened by functional annotation.Transcription factors such as auxin response factor(ARF,AUX/IAA),ethylene response element binding factor(ERF),and leucine zipper(bZIP)were also included in the co-expression network,and these genes may play a crucial role in pericarp development process.

Sowing date and Planting density are two key factors that affect maize yield.In order to clarify the response characteristics of different summer maize cultivars to sowing date and planting density in the Huanghuaihai region.Two maize cultivars Zhongnongda 788 and Kehe 699 were used as test materials.Three sowing dates,June 10,17 and 24,as well as three densities,67 500(A),75 000(B),and 82 500 plants/ha(C)were set and later investigated the growth stages,morphological indexes,yield and yield components.The results showed that the growth process before silking was accelerated and the filling period was prolonged as the sowing dates postponed,maize planted in the third sowing date could not reach physiological maturity.Late sowing date(the third sowing date June 24)compared to early sowing date(the first sowing date June 10),the ear height of Zhongnongda 788 and the plant height,ear height of Kehe 699 increased significantly.The stem diameters of the two cultivars were significantly reduced;the empty stalk and lodging rate of the two cultivars increased with the delayed sowing dates;the yield of Zhongnongda 788 decreased by 21.8% mainly due to the decrease of 1000-kernel weight,the yield of Kehe 699 decreased by 41.3% due to significant reduction of ear number,kernel number per ear and 1000-kernel weight.Compared to density A,the plant height,ear height,empty stalk rate and lodging rate of the two cultivars increased significantly,the stem diameter decreased in density C significantly.Zhongnongda 788 obtained the maximum yield at density B and was significantly higher than density A,which were 12 450,11 097 kg/ha,respectively.With the increase of density,ear number of Kehe 699 didn't increased due to increased empty stalk rate,kernel number per ear decreased,thus yield of density C was significantly lower than density A,which were 7 548,9 464 kg/ha respectively.Interaction between sowing date and density only had extremely significant effect on lodging rate,but had no significant effects on morphological indexes,empty stalk rate,yield and yield components.On the whole,the average yield of Zhongnongda 788 was higher than Kehe 699,the former had lower empty stalk rate,lodging rate and more stable yield under the conditions of late sowing date and high density.In practical production,summer maize should be sown as early as possible,the yield loss caused by late sowing can be reduced by selecting suitable cultivars.To improve yield by increasing density,density resistance cultivar breeding is necessary.

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 explore the germplasm resources of male sterile line and identify the male fertility genes, which would provide the basic materials for the maize seed production by the male sterile line. Using the male sterile mutant x50 as the experimental material,the male sterile phenotype of x50 was studied,and the F₁ and F₂ populations of x50 and inbred line Mo17 were constructed to determine the genetic pattern of the male sterile trait in x50.With the F₂ population,the male fertility gene X50 was identified by the map-based cloning.Furthermore,the candidate gene was confirmed by the allelism test.The results showed that compared with the wild type,the x50 anthers did not emerge from the glume,and was smaller and wilted,and no mature pollen grains were formed.All F₁ plants were fertile,and F₂ plants displayed 3∶1 segregation ratio between fertile and sterile plants,indicating that the monofactorial recessive inheritance of x50.The gene X50 was mapped to the interval from the molecular marker 2-4901 to 2-4963 on chromosome 2 with a physical range of 237.42 to 241.39 Mb by map-based cloning.Candidate gene analysis found that the male fertility gene ZmMs33 was located in the mapping region.In addition,the test crosses of the ms33 mutants(ms33-6029 and ms33-6052)and heterozygous +/x50 revealed 1∶1 segregation ratio between fertile and sterile plants.These results suggested that x50 was an allele mutant of ZmMs33 gene.The identification of the male sterile mutant x50 provided germplasm resources for maize hybrid seed production and functional study of ZmMs33 gene.

Leaf length and leaf area are two important agronomic traits,in order to study the genetic mechanism of leaf length and area of three leaves near the ear in maize,a recombinant inbred line(RIL)population(241 lines)derived from Zheng 58 and D863F was used for QTL mapping analysis under spring sowing and summer sowing in 2018 and 2019,respectively.In RILs population, leaf length and area of three leaves near the ear showed continuous variations with a normal distribution and belonged to typical quantitative trait, and significant correlation was found among the traits, the heritability of the six traits was 88.04%, 88.45%, 87.86%, 85.04%, 85.27% and 85.73%, respectively.In total,23 QTLs were detected in two years.The number of QTLs for leaf length and leaf area were 14 and 9,respectively.These QTLs with phenotypic variance explained(PVE)ranging from 5.84% to 17.81% were detected on chromosome 1,2,4,5,6 and 8.Among them,only three QTLs(qFirLL1-2,qFirLL5-1 and qSecLL1-2)for leaf length and two QTLs(qFirLA2-1 and qSecLA2-1)for leaf area were identified in both environments(spring and summer sowing),the remaining QTLs can only be detected separately in spring sowing or summer sowing environments.The major QTLs controlling six traits were detected on chromosome 2(bnlg1316—bnlg1141)and 5(umc1591—umc2298),which explained phenotypic variation ranging from 6.42% to 17.81%;These two marker intervals are important for regulating the length and area of three leaves near the ear, and might contain key genes regulating leaf traits.

In order to explore the effects of planting density on grain moisture content,dehydration rate and mechanical harvesting quality of different maize varieties,to clarify the dehydration law and mechanical harvesting loss characteristics of maize grains under different densities at harvesting stage,and to provide theoretical basis for determining the appropriate mechanical grain harvesting time under dense planting mode of spring maize.Five maize varieties Zhengdan 958(ZD958),Xianyu 335(XY335),Lishou 1(LS1),Zhongnong 222(ZN222)and Zhongnong 239(ZN239)were used as experimental materials,and planting densities of 60 000,75 000 and 90 000 plants/ha were set.The effects of different density treatments on grain moisture content,dehydration rate and harvesting quality of spring maize were analyzed.The results showed that planting density significantly affected the grain water content at mature stage,and the grain water content of 90 000 plants/ha was significantly lower than that of 75 000,60 000 plants/ha,while there was no significant difference between the two low density treatments.There was a great difference in water content among different varieties,and the water content from high to low in two consecutive years were ZD958>LS1>ZN222>XY335>ZN239.Planting density had no significant effect on dehydration rate,but variety had a significant effect on dehydration rate.With the increase of planting density,the water content and fragmentation rate of seed decreased.The results showed that ZD958 and XY335 were not suitable for local mechanical harvesting,while LS1,ZN239 and ZN222 were suitable for local mechanical harvesting.The optimum density is from 75 000 to 90 000 plants/ha.

The aim of this research was to screen the appropriate planting density for double ear type waxy new maize variety Wancainuo 88 and explore the potential to achieve increased yield,field experiment was carried out to study the important plant traits,double ear rate,yield and yield component traits of Wancainuo 88 compared under the different planting densities.The study results showed that as planting density increased,the plant height,ear height,dual fruits silking interval and second ear silkingx-anthesis interval all increased,while the first ear silking-anthesis interval and double ear rate decreased.The planting density indirectly or directly affected to the double ear rate by changing the dual fruits silking interval,first ear silking-anthesis interval and second ear silking-anthesis interval.There were significant or highly significant responses of yield and its component traits for the first ear and second ear to planting density,except for the ear rows and ear length of first ear.With the planting density increased from 30 000 to 60 000 plants/ha,the first fresh ear yield,overall fresh ear yield,first fresh grain yield,overall fresh grain yield were increased 5 366.10,3 465.98,3 302.85,2 165.60 kg/ha,respectively.The second fresh ear yield and fresh ear yield were decreased 1 900.12,1 137.25 kg/ha,respectively.There was not significant for overall fresh ear yield and overall fresh grain yield among the 48 000,54 000,60 000 plants/ha,but extremely significant higher than the other planting density.Based on the above research results,the optimal planting density for new variety Wancainuo 88 was 48 000 plants/ha could be initially used for field planting.

In order to clarify the effects of high temperature stress during grain filling stage on leaf senescence and yield,a field experiment from 2019 to 2020 was conducted with employing heat-sensitive variety(XY335)and heat-resistant variety(ZD958). Simple plastic greenhouse was constructed for heat treatment(HT)during 12-25 days after silking,the natural temperature was set as control(CK). The two years results showed that from 12 to 25 days after silking,high temperature stress significantly reduced the grain weight and yield of summer maize. For ZD958,the grain yield of HT was reduced by 18.8% and 19.3% than CK and thousand kernels weight(TKW)was decreased by 23.4% and 9.1%,respectively.For XY335,the grain yield and TKW of HT were reduced by 29.4%,26.3% and 20.1%,14.2%,respectively.High temperature during grain-filling stage accelerated leaf senescence. The two years results showed that leaf senescence rate(LSR)of ZD958 and XY335 under HT were increased by 76.4%,140.6% and 135.1%,139.6%,respectively.Leaf area duration(LAD)after silking with HT was reduced by 17.7%-36.5% compared with CK. Ear leaf photosynthesis under HT was lowered by 20.0%-42.9% than CK.Correlation analysis results indicated that accelerated LSR under HT had negative correlation with grain yield but without statistical significance(P=0.064 7).LAD after silking,photosynthesis,and SPAD significantly reduced under HT,which showed significant positive correlation with grain yield(P< 0.05). Taken together,heats tress during grain filling significantly accelerated leaf senescence,thus lowering kernel weight and resulting in yield loss. Under high temperature stress,heat-resistant maize variety had higher regulation ability than high temperature-sensitive maize variety,which could significantly mitigate yield loss caused by high temperature stress.

A field experiment was conducted to investigate the inter-specific competitive interaction between Ageratina adenophora and Zea mays and to explore the methods of controlling the invasive weed A.adenophora by replacing growth of Z.mays,and then meet the combination of grain crop production and weed control.Tillage methods,cutting ways for A.adenophora and different density of Z.mays were considered.Plant height,density and competitiveness for light,nutrients(e.g.N,P,K)and water of A.adenophora and Z.mays as well as the yield and market values of Z.mays were investigated to evaluate the competition effects between A.adenophora and Z.mays.Results showed that A.adenophora was the dominant population and the growth and yield of Zea mays were inhibited when Z.mays seeds were sown between the plant gaps of A.adenophorum without tillage.However,Z.mays became the dominant population companioned with a significant competitive advantage of light and nutrients usage when Z.mays seeds were sown after cutting or removing A.adenophorum without tillage.And moreover,the growth of A.adenophorum was inhibited,and the absorbed nutrients and water were significantly reduced.The invasive weed A.adenophora was displaced completely by Zea mays within rotary tillage treatment and the yield of Z.mays reached 9 774.0 kg/ha.The results indicated that through reasonable agronomic cultivation measures,the use of corn replacement could not only effectively prevent and control Eupatorium adenophorum,but also produce considerable ecological benefits.Hence,it has certain theoretical and practical significance for the research and development of effective comprehensive prevention and control technology of Eupatorium adenophorum.

In order to clarify the characteristics of the effect of increasing plant density on the source-sink relationship of maize,ZD958 and JQ119 were chosen as the experimental materials,and five different planting densities (45 000,60 000,75 000,90 000 and 120 000 plants/ha) were set to explore the response characteristics and changes of plant morphology,leaf canopy photosynthetic characteristics and establishment of grain sink of different hybrids at anthesis of maize to increase plant density. The results showed that with the increase of plant density,plant height,ear height and ear coefficient increased significantly. The basal intersegmental diameter Ⅲ,the extinction coefficient (k),the leaf area per plant and the ear leaf area of maize were significantly decreased,and the net photosynthetic rate of ear leaf,photosynthetic capacity of ear leaf and kernel number per ear were the same as above. The effects of increasing of plant density on different maize hybrids were generally consistent. When plant density was increased from 45 000 to 120 000 plants/ha,the ear leaf area decreased by 20.63% and 12.30%,the photosynthetic capacity of ear leaf decreased by 33.76% and 33.31%,and the kernel number per ear decreased by 21.55% and 36.07%for ZD958 and JQ119,respectively.The linear relationship between photosynthetic capacity of ear leaf,kernel number per ear and plant density was further established. The linear relationship showed that for every 1×10⁴ plants/ha increase in plant density,the photosynthetic capacity of ear leaf of ZD958 decreases by 0.076 μmol/s and the kernel number per ear by 13.03,while the photosynthetic capacity of ear leaf of JQ119 decreases by 0.088 μmol/s and the kernel number per ear by 27.93.From the linear slope,compared with ZD958,JQ119's leaf source and grain sink were more sensitive to increasing plant density,and the difference between the two hybrids was mainly manifested in the establishment of grain sink. In addition,this linear model can be applied to the simulation and prediction of maize canopy photosynthetic characteristics and grain sink establishment by increasing plant density,which can provide reference for moderately increased plant density for high yield of maize.In summary,enhancing the source and expanding the sink is the key to increasing yield in summer maize under increasing plant density.

Corn stalk rot is harmful to yield and quality of corn,so effective control of corn stalk rot should be carried out as soon as possible.For Fusarium graminearum,the dominant strains of corn stalk rot in Jilin Province,and fourteen Trichoderma sp.strains were isolated from corn rhizosphere soil were subjected to plate confrontation experiment respectively.By observing the inhibitory effect of Trichoderma sp.strains on Fusarium graminearum,the strains of CCTH-2 and CCTH-6 with better inhibitory effect could be screed.The inhibition of Fusarium graminearum by fermentation broth,volatile metabolites and non-volatile metabolites of these two Trichoderma sp.strains were screened again,and inhibitory effect of these two Trichoderma sp.strains on other pathogens.Finally,Trichoderma sp.strain CCTH-2 with good control effect was screened by comprehensive analysis.Morphological and molecular identification showed Trichoderma harzianum,and its biological characteristics were preliminarily studied.The results showed that the inhibition rate of CCTH-2 against Fusarium graminearum was 82.83% under culture conditions of slab face-off method and the fermentation broth,volatile metabolites and non-volatile metabolites of CCTH-2 against Fusarium graminearum was 36.56%,46.75%,32.48%,showed significant inhibition effect.The biological characteristics test showed that PDA was the optimal medium for the growth and sporulation of CCTH-2 colonies,the optimal temperature was 25 ℃,the optimal illunination condition was total illumination,exogenous addition of Fe²⁺ was beneficial to the growth and development of CCTH-2,and CCTH-2 had the ability to adapt to the changes of pH value and salt contene.Therefore,it could be confirmed that Trichoderma harzianum CCTH-2 was a biocontrol bacterium with good control effect and great potential,providing information guarantee and theoretical basis for the subsequent development and utilization of biocontrol bacteria of corn stalk rot.

In order to preliminarily explore the key regulatory networks and genes involved in maize cold resistance,identify the key regulatory pathways and genes in response to low temperature stress,which laying a foundation for further research on the molecular mechanism of cold stress resistance.Here,a cold tolerance variety Mintian 6855 was employed to determine the gene expression pattern at 24,48 and 72 hours post low temperature of 5 ℃ stress by using transcriptome technique.The PCA analysis revealed that the repeated samples were well clustered together and significantly separated from CK samples.The results of difference analysis showed that about 4 000—7 000 difference genes expressed after cold stress treatments,while,only about 100—2 000 showed difference expressing among low temperature treated samples,indicating that low temperature was the main factor results in genes difference expressing,and the difference expression genes were mainly responded in the early stage.Meanwhile,KEGG annotation analysis results revealed that the differentially expressed genes were enriched in pathways of plant hormone signal transduction and MAPK,suggesting that these two signaling pathways actively respond to cold stress.In addition,different express genes were also enriched in plant-pathogen interaction as well as circadian rhythm plant,strongly implied that there were overlapping or common regulatory pathways in biological and abiotic stress pathways,while,genes that regulate circadian rhythms also playing a key role in plant adaptation to low temperatures.

In order to explore the responses of kernel position effect of summer maize to plant density and its carbon and nitrogen metabolism characteristic,field experiments were conducted during 2020 and 2021 growing reasons at Dishang Experimental Station,Institute of Cereal and Oil Crops,Hebei Academy of Agriculture and Forestry Sciences. Three plant densities(PD1:60 000 plants/ha;PD2:75 000 plants/ha;PD3:90 000 plants/ha)were arranged,with the objectives to study the effect of plant density on grain filling and kernel weight ratio of inferior and superior kernel and its physiological characteristics of carbon and nitrogen metabolism. Compared with the superior kernel,the response of inferior kernel to plant density was more obvious,significant differences in grain-filling rate and kernel weight of inferior kernel were observed since 20—25 d and 30—35 d after pollination,respectively. As the plant density increases,the kernel weight ratio of inferior to superior kernel significantly decreased,PD3 decreased the kernel weight ratio of inferior to superior kernel by 8.45% on average,compared to that of PD1. The single plant dry matter accumulation significantly decreased as the plant density decreased,this was mainly due to the significant decrease of post-silking dry matter accumulation. The analysis of carbon and nitrogen metabolism of kernel showed that the increased plant density exacerbate the difference in starch and protein contents between inferior and superior kernels;and the increased plant density also exacerbate the difference in SPSase,ADPGase and GS activities between inferior and superior kernels,which mainly attributed to the significant decrease in SPSase,ADPGase and GS activities of inferior kernel. In conclusion,the increased plant density exacerbate the kernel position effect of summer maize,this was related to the lower grain-filling rate and kernel weight of inferior kernel since mid-grain filling stage,the lower grain filling rate in inferior kernel under dense planting was not only related to the insufficient post-silking dry matter accumulation,and it was also closely related to the lower activities of SPSase,ADPGase,and GS in inferior kernels.

In order to explore the effects of the combination of nitrogen application rate and nitrogen application period on the photosynthetic characteristics,senescence characteristics,grain filling characteristics and yield of leaves at ear position of summer maize under the integrated condition of drip irrigation,summer maize variety Zhengdan 958 was selected as the test material.Under the condition of 210 kg/ha,top dressing treatment at jointing stage,belling stage and flowering stage(A1),top dressing treatment at jointing stage and belling stage(A2),top dressing treatment at jointing stage and flowering stage(A3);under the condition of 180 kg/ha,top dressing treatment at jointing stage,belling stage and flowering stage(A4),top dressing treatment at jointing stage and belling stage(A5),top dressing treatment at jointing stage and flowering stage(A6);the traditional border irrigation was set as the control CK,and the total nitrogen application was 240 kg/ha,CK1 was topcoated with nitrogen fertilizer at jointing stage at one time,and CK2 was topcoated with nitrogen fertilizer at jointing stage and belling stage respectively,with a total of 8 treatments.The results showed that compared with CK1,A1 and A4 treatments not only maintained LAI and SPAD values in the late growth stage of summer maize,but also significantly increased the activity of antioxidant enzymes(SOD,POD and CAT),and effectively inhibited the content of peroxide MDA,so as to delay the aging process of its leaves and protect the functional structure of leaf cells.Therefore,the summer maize under this treatment maintained efficient photosynthetic characteristics in its later growth stage,promoted the grain filling rate,and then increased the number of grains per ear and 1 000 grains weight,so that the maize yield was significantly improved.The yield difference between A1 and A4 treatments was not significant difference,but the nitrogen application rate of A4 was reduced by 14.3% compared with A1,which reduced the input of nitrogen fertilizer and saved the input cost.It was the recommended treatment in this experiment.

In order to further reveal the decomposition process and mechanism of corn straw in the cold area under the application of low temperature straw degrading agent,and provide a new strategy and theoretical basis for the decomposition and comprehensive utilization of straw in the cold area.Corn straw was decomposed by low temperature straw degrading agent and its physical and chemical characters and microbial diversity were analyzed.According to the change of temperature in the fermentation process,the ripening process of corn straw was divided into five stages:initial stage(A1),heating stage(A2),ripening stage(A3),stable stage(A4)and cooling stage(A5).The monitoring results of the physical and chemical properties of corn straw in different maturity stages were as follows:with the extension of maturity time,the fiber bundles on the surface of corn straw were destroyed gradually.After maturity during the cooling stage,the relative content of cellulose and hemicellulose in corn straw decreased to 33.48% and 16.57%,respectively,while the content of total nitrogen and ammonium nitrogen in corn straw decreased at first and then increased,and the contents of organic matter decreased to 149.7 g/kg.The monitoring results of microbial diversity in the fermentation stacks were as follows:Guehomces were the most abundant and dominant species in the ripening process;Pseudomonas and Sphingobacterium were the main genera in the initial and ripening stages,and thermophilic microorganisms played a major role in the heating,stationary and cooling stages of ripening.The changes of physical and chemical properties and microbial diversity in fermentation stack of corn straw after the application of low temperature straw degradation agent in cold area were clarified.