Zeaxanthin is a carotenoid pigment, which was named from maize where it was first extracted. Because it couldn’t be synthesized by human, and it was obtained only from daily dietary food, and could not only protect eyes, but also played an important role in the prevention of aged-related macular degeneration (AMD, the leading cause of blindness), cataract, cardiovascular diseases, cancer and so on, people paid more attention to zeaxanthin in crops. In this study, the properties and source of zeaxanthin, its physiological functions and its biosynthesis pathway were summarized according to new progress. Moreover, its extraction, measurement methods and application in food industry were also reviewed. In addition, studies on zeaxanthin-rich crops were discussed.

【Objective】The objective of this study is to screen Trichoderma strains which have inhibitory effect on the Pythium spp. causing maize stalk rot, and to clarify their taxonomic status, control efficacy and antifungal mechanism. This study will provide important resources for the research and development of biocontrol agent against Pythium stalk rot.【Method】For the antagonistic strains screening, the inhibitory effect of Tichoderma strains on P. inflatum, P. arrhenomanes and P. aristosporum was tested by measuring the mycelia growth. The taxonomic status of Tr21 was determined by morphological and molecular characteristics. The effect of Tr21 on the mycelia morphology of Pythium spp. was observed in the laboratory. In order to analyze the effect of Tr21 fermentation broth on the membrane permeability of Pythium spp., propyridine bromide (PI) dye solution was used to stain, and the absorbance values of protein and nucleic acid in mycelia supernatant at different treatment times were detected. The effect of Tr21 fermentation broth on germination characteristics of maize seeds was tested by seed soaking with different concentrations of fermentation broth. The control efficacy of Tr21 on stalk rot was confirmed through greenhouse pot and field inoculation experiments.【Result】From the 109 strains of Trichoderma spp., seven strains were screened with antagonistic activity against P. inflatum, P. arrhenomanes and P. aristosporum, and the inhibition rate was above 60%. The inhibition rate of Tr21 to three Pythium species reached 100%, the inhibition rate of 5×, 10× and 20× diluent to three Pythium species reached 100%, and the inhibition rate of 50× diluent to three Pythium species was also more than 55.56%. Tr21 strain was identified by morphological and molecular biology as T. afroharzianum. The results of microscopic observation showed that the fermentation broth of Tr21 could cause mycelial malformations, such as rough mycelia, increased mycelial branching, shortened nodes, and overflow of mycelia contents. The result of PI fluorescence stain showed that the cell membrane of three Pythium species was damaged by Tr21 fermentation broth, and the PI dye was more likely to penetrate the damaged cell membrane into the mycelium and stain the mycelia red. The results of nucleic acid and protein leakage showed that the absorbance values of the mycelia treated by the fermentation broth changed greatly. After treatment for 5 h, the OD₂₆₀ increased by 0.08 and OD₂₈₀ increased by 0.10, 0.11 and 0.10, respectively, indicating that the membrane of the mycelia was damaged, leading to the overflow of mycelia contents. The different concentrations of Tr21 fermentation broth had no effect on the germination characteristics of maize seeds, and the 20× diluent had the best effect on germination and growth of seeds. The results of pot experiment showed that 5× diluted fermentation broth of Tr21 had the best control efficacy on Pythium stalk rot caused by three Pythium species, which was 60.67%, 63.15% and 59.66%, respectively. The control efficacy on Pythium stalk rot of 5× diluent was the highest, reaching 82.25%, with a mass ratio of 1﹕100 (5× diluent to seed).【Conclusion】An effective T. afroharzianum strain Tr21 was obtained for preventing and controlling of maize Pythium stalk rot. The fermentation broth of Tr21 can lead to mycelia malformation, breakage, cell membrane damage and contents leakage, etc. In conclusion, the T. afroharzianum strain Tr21 is a promising biocontrol microbial.

Maize is one of the most important grain crops in the world. Improving the kernel quality of maize is a highly concerned problem in the field of maize breeding worldwide. The traditional and conventional breeding methods have the limitations of long breeding time and low transformation rate, so the most economical and effective way to solve this problem is to use molecular marker assisted selection breeding. In order to provide reference for molecular design and breeding of maize quality traits in the future, this study summarized relevant research progress of QTL mapping, molecular marker assisted improvement, candidate gene cloning and transgenic technology application of maize kernel quality traits at home and abroad. Based on the review, the study points out that the utilization of high-quality gene resources in maize is not sufficient, and the application of existing molecular marker technology in maize breeding is not extensive enough. In the future, breeding methods and quality identification techniques should be improved to shorten the breeding cycle of maize.

To have a comprehensive and in-depth understanding of the current situation and development trend of researches on maize planting density and yield at home and abroad, 5150 pieces of literature on maize planting density and yield collected from the CNKI database and Web of Science Core Collection database from 2000 to 2022 were taken as samples for visual analysis based on CiteSpace software. The results showed that the United States ranked first in the total research volume in this field, followed by China, far beyond other countries. In recent years, China had overtaken the United States in the number of research papers in this field, and kept more than 100 articles published every year. Agronomy Journal had the largest number of publications, with a total of 230 papers, and had the largest influence in academic circles. Chinese scholar Liu Peng published the most papers, made the greatest contribution to the research progress in this field, and cooperated closely with other authors. The research institutions were mainly universities, mostly in northern China, and the cooperation among regional institutions needed to be strengthened. In this field, special corn such as fresh food and silage corn, water and nitrogen utilization efficiency, sustainable agriculture, mechanized management, soil properties, yield loss, mathematical model, straw utilization, and so on are the hot research issues in recent years.

In field production, new maize varieties with U.S. germplasm such as ‘Xianyu 335’ are weak in resistance to dense planting, lodging, Southern Corn Rust, leaf blight, and high temperature and heat. To solve these problems by means of plant breeding, we use maize new variety ‘Yufeng 303’ as the test material to study its performances, including yield performance, drought tolerance, high temperature and heat tolerance, dense planting resistance, and grain quality at production trials, at national trials (Huang-huai-hai Summer Maize Area, Eastern of North China Middle and Late Maturity Spring Maize Area, and Northwest Spring Maize Area) and provincial trials. The results show that ‘Yufeng 303’ not only possesses the desirable traits of new maize varieties with U. S. germplasm, but also has traits of high tolerances to drought, high temperature and heat, lodging, and Southern Corn Rust, achieving and substantially surpassing our original breeding goal. Based on these results, several issues for future breeding, including the general technical route of germplasm expansion, improvement and innovation, the avoidance of genetic vulnerability risk and others related to commercial breeding, are discussed. The study emphasizes the importance of breeding the traits of high temperature tolerance and drought tolerance, especially the importance of breeding new varieties with wide stress adaptability by constantly uplifting the positive super normal expression of genotype environment interaction.

Research on forage maize can effectively promote the development of animal husbandry. In order to accelerate the progress of forage maize, this paper reviewed the regulation mechanism and breeding process of quality protein maize. Meanwhile, the characteristics and breeding process of high protein silage maize were introduced in detail. The problems existing in the development of quality protein maize and high protein silage maize were pointed out, and some relevant suggestions were put forward in order to promote the structural reform of maize from food crop to feed crops in China.

In view of the shortage of water and heat resources in different ecological areas, and the frequent occurrence of wind disaster, lodging, low yield, poor quality and other problems in maize production, a new maize variety ‘MC278’ was bred by taking ‘Jing X005’ as female parent and ‘Jing 27’ as male parent. The inoculation tests of the variety in Jilin, Hebei and other places showed that it had strong resistance to small spot disease, Curvularia, dwarf mosaic, silk smut and stem rot, and was easy to infect large leaf spot, and it was moderately resistant to corn borer in Jilin. In the regional trials in Beijing, Inner Mongolia and other regions in different years, the kernel yield of ‘MC278’ was significantly higher than that of ‘Zhengdan 958’ (CK), the highest yield was 16166 kg/hm², and the average yield was increased by 8.3%. The content of crude protein, crude starch and lysine of ‘MC278’ were significantly higher than those of ‘Zhengdan 958’. In 2019, the production in Hebei, Shanxi, Inner Mongolia and other regions showed that the yield of ‘MC278’ was all more than 12804 kg/hm², and the maximum yield was 14283 kg/hm². ‘MC278’ was equipped with field management measures and harvest techniques, such as suitable sowing date, density and water and fertilizer management, and prevention and control measures of diseases and insect pests. The variety passed the national examination and approval in 2019 (National Approved Maize Variety No.20190030), and its planting area now includes 15 provincial regions, such as Anhui, Shanxi, Shandong and etc.

【Objective】 Mining the key drought-resistant genes of maize, revealing its drought-resistant molecular mechanism, and providing genetic resources and theoretical guidance for the cultivation of new drought-resistant maize varieties.【Method】Transcriptome data combined with weighted gene co-expression network (WGCNA) and screening methods for physiological and biochemical indicators of drought resistance were used to identify ZmPAL genes associated with drought resistance and rewatering. Genome-wide analysis of the genes encoding PAL was performed using bioinformatics methods. Quantitative real-time fluorescence PCR (qRT-PCR) was used to detect the expression of ZmPAL genes under drought treatment conditions, as well as the expression characteristics of ZmPAL5 among different inbred lines and the expression patterns in different tissues. Finally, genetic transformation was used to analyze the drought resistance function of ZmPAL5 in maize, and the deletion-type Arabidopsis mutant was analyzed for drought resistance with the help of CRISPR/Cas9 technology for the PAL5 homologous gene.【Result】Nineteen maize ZmPAL genes were identified, six of which were clustered on chromosome 5 and encoded proteins that were mostly hydrophilic acidic proteins and relatively evolutionarily conserved in the PAL family of genes. The promoter region of ZmPAL genes contained a large number of cis-acting elements associated with hormonal and abiotic stress responses. Six core genes were identified, four of which were significantly up-regulated for expression after drought treatment. In particular, ZmPAL5 showed an 8.57-fold increase in expression after drought stress. The expression level of ZmPAL5 was found to be significantly higher in the drought-resistant inbred line Zheng 8713 than in the drought-sensitive inbred line B73 under both drought stress and rewatering treatments. Meanwhile, ZmPAL5, a constitutively expressed gene, showed a high level of expression in young stems. Overexpressed ZmPAL5 maize grew well under drought stress, and its relative water content, lignin, chlorophyll, soluble protein, proline content, and activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase were 1.52, 1.49, 1.47, 1.43, 1.44, 1.41, 1.53, 1.41, and 1.35 times, but the malondialdehyde content was 0.65 times that of the wild type. The PAL5-deficient Arabidopsis mutant was sensitive to drought. Under drought stress, its physiological and biochemical indexes showed the opposite trend to those of overexpression of ZmPAL5 maize. 【Conclusion】 Six core genes (ZmPAL3, ZmPAL5, ZmPAL6, ZmPAL8, ZmPAL11, and ZmPAL13) were screened in response to drought stress, in which the expression of ZmPAL5 was positively correlated with drought resistance. ZmPAL5 positively regulated the drought resistance and resilience of the plant by influencing the content of osmotically regulated substances and antioxidant enzyme activities.

【Objective】 Maize ear rot caused by Fusarium verticillioides is one of the most serious diseases in maize producing areas in China. The objective of this study is to understand the differences in gene expression during the plant-pathogen interaction at different stages, and to provide a basis for pathogenic mechanism of the pathogen infection and resistance mechanism of maize. 【Method】 Illumina platform was used to sequence the transcriptome of maize kernels infected with F. verticillioides at 0, 4, 12, and 72 h. The differentially expressed genes (DEGs) of maize and F. verticillioides were screened with |log₂FC|≥1, P-adjust<0.05 as threshold and clean reads were compared with genome of maize and F. verticillioides, separately. Functional annotation and enrichment analysis of DEGs were carried out by using GO and KEGG databases. Goatools software was used to analyze the expression changes of genes related to plant-pathogen interaction, MAPK signaling pathway and plant hormone signal transduction pathway. Sequencing results were verified by quantitative real-time PCR (qRT-PCR). 【Result】 A total of 140, 400 and 1 945 DEGs were up-regulated and 9, 302, and 1 784 DEGs were down-regulated in F. verticillioides after 4, 12 and 72 h interaction, respectively. A total of 293, 692, and 1 426 DEGs were up-regulated and 320, 482, and 153 DEGs were down-regulated in maize after 4, 12 and 72 h interaction, respectively. GO and KEGG enrichment analysis of DEGs showed that F. verticillioides grew in intercellular space at the early stage of pathogen infection. The DEGs were enriched in RNA biosynthesis, cell wall structural component, fatty acid biosynthesis, protein metabolism, carbohydrate metabolism, biological process, and metabolic process. Reactive oxygen species (ROS) was triggered in maize at the early stage of infection. The DEGs were enriched in response to ROS, hydrogen peroxide, chitinase activity, monooxygenase activity, lignin metabolism. At the later stage of infection, F. verticillioides colonized and expanded in maize, and the DEGs were enriched in carbohydrate and cell wall polysaccharide catabolic process, transmembrane transport and oxidoreductase activity. Maize responded to pathogen infection through phenylpropanoid, lignin, flavonoid biosynthesis, MAPK signaling pathway, plant-pathogen interaction and plant hormone signal transduction. Six DEGs of maize and six DEGs of F. verticillioides were randomly selected for qRT-PCR. The results were consistent with those of transcriptome sequencing, which confirmed the accuracy of RNA-seq. 【Conclusion】 At the early stage of infection, F. verticillioides grew in the intercellular space, triggering ROS outbreak in maize and the expression of related pathway differential genes. At the middle and late stages of infection, the pathogen further colonized and expanded in maize with starch as nutrient. Maize responded to the infection of F. verticillioides through biosynthesis of phenylpropanoid, lignin and chitinase. Meanwhile, plant-pathogen interaction, MAPK signaling pathway, and plant hormone signal transduction were involved in the resistance to the infection of F. verticillioides.

In order to promote the application of molecular marker-assisted selection in maize breeding, the research progress of QTL of kernel yield of maize and its components’ traits in recent 30 years was summed up. The results showed that there were 5-9 QTLs for kernel yield, and they were mainly distributed on chromosome 1, 2, 5, 6, 7, 8 and 9. There were 3-6 QTLs for the kernel row number, kernel number per row and 100-kernel weight, and they were mainly distributed on chromosome 1, 2, 3, 4, 5, 6, 7 and 8. These QTLs were distributed in clusters on several main chromosomes and formed QTL enrichment regions, and they could explain about 25% of the phenotypic variation in traits. QTLs of most traits mainly manifested as additive, dominant, partial dominant or superdominant effects, and QTLs of some traits showed genetic × environment interaction. It indicated that QTLs of kernel yield and its components’ traits had common chromosomal carriers, the breeding selection should be carried out in multiple environments and with large number of samples, and those QTLs that could be expressed stably in different environments were more suitable for breeding selection. The QTL study on ear number per plant, plant traits and stress resistance should be strengthened.

By exploring the changes in the research field of fresh-eating corn in China, grasping the research status and hot topics, and discussing the research frontiers and development trends, the study aims to provide theoretical reference for the research of fresh-eating corn. The research team used 1588 fresh-eating corn research literature in the CNKI database from 2010 to 2021 as the research objects, and carried out visual quantitative analysis based on CiteSpace software. In the past 10 years, the research development in the field of fresh-eating corn was stable, and the number of core papers published per year remained above 100. The high-yield authors were represented by LU Weiping, LIU Chunquan, LI Dajing, LU Dalei, etc., presenting single-line or radial team cooperation. The institutions to which the authors belong were mainly agricultural colleges and universities and scientific research institutes. Agricultural colleges and universities achieved more significant results in terms of the number of publications, and scientific research institutes had more advantages in the research and development of new varieties, and scientific research institutions and universities had close team cooperation. The analysis of emerging words indicates that haploid, super sweet corn, seed germination, genetic diversity, nutritional quality, flavor, folic acid, soluble sugar, etc. are the research trends. The core task of future fresh-eating corn research will be expanding the research coverage, breaking through the traditional limitations, exploring gene editing technology, transgenic technology, gene sequencing, single-celled sequencing, genome, proteins, transcription and other cutting-edge biotechnologies which are auxiliary means for traditional fresh-eating corn breeding research, and the focus will be on sweet and waxy corn and super sweet corn research. The future research should also highlight the quality and nutrition of fresh-eating corn varieties, and improve their resistance to diseases and insects, lodging, drought and other stresses. In the fields of food processing and feed research, more attention should be paid to the technology development of new processing equipment for extending the harvesting period and storage period of fresh-eating corn and maintaining the nutrition of corn during storage.

To well understand the function of key enzymes and regulatory mechanism in starch synthesis, we reviewed the starch structure, starch synthesis process, expression profiles and functional mechanism of transcription factors for starch synthesis, including DOF family, NAC family, MYB family, bZIP family, MADS-BOX and AP2/EREB family. Researches show that most of the transcription factors are expressed in maize endosperm, and a few are expressed in maize leaves. Furthermore, these transcription factors could regulate starch synthesis by binding to the promoters of starch syntheses encoding genes and key regulatory genes to affect their expression. In addition, sucrose/ABA and sucrose/IAA with transcription factors also coordinately regulate the starch synthesis. Collectively, this research will not only enrich the knowledge of the regulating mechanism in maize starch synthesis, but also supply reference for breeding new maize varieties.

To adapt to dense planting of maize and meet the rapid mechanization development of agricultural production, the basic maize population was developed by using abroad excellent germplasm materials, then high-density and large-population selection, targeted inoculation and identification methods were adopted to obtain the new variety ‘Ruipu909’ with the disease-resistant self-line ‘RP86’ as female parent and ‘RP06’ as male parent. This variety has characteristics of density resistance, stress resistance, high yield and easy mechanical harvesting. The results show that the average yield of the regional test is 12589.5 kg/hm ², 7.1% higher than that of the control variety. There are 111 test points, the yield-increase points accounted for 93%. The yield of production test is 12601.5 kg/hm ², compared with the control variety, the yield increased by 7.7%, and there are 95% yield-increase points among the 54 test points. The average lodging rate in regional and production tests is 1.6%. ‘Ruipu909’ is resistant to northern corn leaf blight, stalk rot and ear rot. The crude starch content of seeds is 75.24%. In summary, the new variety ‘Ruipu909’ has multiple characteristics of high and stable yield, strong disease and lodging resistance, good quality, wide adaptability, density resistance and is suitable for mechanical harvesting. The variety was examined and approved by Shanxi Province in 2017 and was further approved by Shaanxi, Inner Mongolia and passed the national authorization in 2018. The variety is suitable for popularizing and planting in middle-late maturing areas of spring sowing regions in eastern north China and northwest China and Huanghuaihai summer maize areas in southern Shanxi.

【Objective】 Plant height is one of the important target traits in maize plant type breeding, which is closely related not only to mechanized grain harvesting and lodging resistance, but also to maize yield. Therefore, it is of great theoretical and breeding value to isolate QTL/gene of maize plant height and analyze its function. This study aims to locate a novel maize dwarf gene ZmDLE1, clarify its biological function, and provide important theoretical basis and gene resources for accelerating the improvement of maize plant type. 【Method】 A single recessive mutant was derived in maize inbred line LY8405, from Crop Research Institute of Gansu Academy of Agricultural Sciences, by chemical mutagenic agent Ethyl Methyl Sulfonate (EMS). A maize dwarf and low ear mutant was isolated from the M₂ progeny, and the M₃ and M₄ progeny could stably inherit, which was named dwarf and low ear mutant1 (Zmdle1). The F₂ population was constructed by hybridization with Mo17 and was identified by bulked segregate analysis-sequencing (BSA-seq) and target segment recombination exchange. Based on the Mo17 reference genome, the genes in the target region were obtained and functionally annotated to locate candidate genes.【Result】Phenotypic identification of Zmdle1 was carried out, and the phenotype of Zmdle1 at seedling stage was not significantly different from that of the control LY8405. The plant height and ear height of Zmdle1 at mature stage were reduced by 87.2 cm and 55.4 cm, respectively, accounting for about 35.0% and 62.9%, difference is extremely significant. Morphological observation showed that the decrease of internode number and the shortening of internode cell length were the main reasons for the significant decrease of plant height and ear height of Zmdle1. The genetic analysis of the mutant gene was conducted by using the F_2:3 genetic populations. The Zmdle1 mutant is inherited in a 3﹕1 (χ²=2.854) ratio and is a single recessive gene. Therefore, according to the results of BSA-seq, the candidate gene ZmDLE1 was initially located in the 15 Mb region of Bin1.09-1.10 on chromosome 1 of maize. The polymorphism molecular markers were further developed using the re-sequencing results of Mo17 and Zmdle1, and the target gene was accurately cloned by map-based cloning. Finally, the candidate genes were mapped to the size range of 600 kb, and there were 16 candidate genes in this range. By comparing the re-sequencing data, it was found that Zm00001d033231 gene changed into A at the 2062 position G, which resulted in amino acid changing from glycine to serine, and the transcription level expression was significantly reduced compared with LY8405. Zm00001d033234 changed from T to C at the 223rd position leading to the 75th amino acid changed from serine to proline, and there was no significant difference in transcription level. Through association analysis of natural populations and the predicted genes for functional annotation, it was found that Zm00001d033231 and Zm00001d033234 were related to the growth and development of maize. 【Conclusion】 The candidate gene ZmDLE1 in the Bin1.09 region at the end of chromosome 1, was identified to effectively regulate maize plant height and ear height, and the target region was reduced to 600 kb by fine localization. Association analysis showed that Zm00001d033231 was genetic locus significantly associated with plant height within the target region.

【Objective】In the context of intensified global climate change and frequent meteorological disasters, exploring the significance of meteorological factors on maize yield and accurately predicting maize yield is crucial for enhancing agricultural production and field management. This paper aims to quantitatively analyze the importance of meteorological factors during various growth stages of maize on yield and to establish a highly accurate and reliable maize meteorological yield stacking ensemble learning estimation model for yield prediction.【Method】Using the HP filter method and moving average method, trend yield models for various counties were determined, and county-level meteorological yields were isolated. Three ensemble learning methods (light gradient boosting machine (LightGBM), Bagging, and Stacking) were employed. By analyzing daily meteorological data and maize yield data over 34 years from 596 county-level administrative regions and meteorological observation stations across 12 provinces in China, three maize meteorological yield prediction models based on different ensemble learning frameworks (LightGBM, Bagging, and Stacking) were established.【Result】The HP filter method as the trend yield model was mainly applicable in the regions of Shaanxi, Henan, Jiangsu, and Anhui. Compared to the HP filter method, more counties were suitable for the moving average method, with most counties having the R² distribution above 0.8. Based on a 5-year sliding forecast and model accuracy evaluation indicators, the mean absolute percentage error (MAPE) for the three models on maize yield was below 6%. The Stacking model achieved a MAPE of 4.60%, indicating high prediction accuracy and strong generalizability. The results demonstrate that the maize meteorological yield stack-integrated learning prediction model has higher accuracy and stronger robustness. It effectively utilizes the characteristics and advantages of each base learner to improve prediction accuracy, making it the optimal model for predicting maize yield based on meteorological factors. Furthermore, a quantitative analysis of the impact of 27 meteorological factors during the maize growth stages in 12 provinces, using the random forest feature importance score, is of reference value for crop monitoring and field management.【Conclusion】The three ensemble learning methods, especially the stack-integrated learning model (Stacking), can accurately reflect the spatiotemporal distribution changes in maize yield. The stack-integrated learning model for maize yield based on meteorological factors provides a new method for field management and accurate prediction of maize yield.

Under the background of the structural reform of agricultural supply side, through the empirical analysis of the purchase intention of Shanghai local brand fresh corn and its influencing factors, the study aims to better promote the brand building of fresh corn and provide the corresponding advices for guiding the consumption of local brand fresh corn. Through the establishment of multivariate and orderly Logit model, we quantitatively analyzed the individual characteristics, family characteristics of different consumer groups, the cognitive characteristics of consumer groups on fresh corn and the dietary preferences of consumers on the purchase intention of Shanghai brand fresh corn products and the direction of action. The results showed that: the gender, age, place of birth, education, consumer willingness to treat fresh corn as a snack, the awareness of the fresh corn production in Shanghai, the trust in the quality and safety of fresh corn products, and the place of origin were significant factors influencing consumers’ willingness to purchase local brand fresh corn. On the whole, the current information asymmetry between the market and consumer is still an important factor restricting the development of local brands and the consumption of high-quality agricultural products. Based on this, we put forward targeted suggestions from the precise positioning of consumer groups, reducing information asymmetry between market and consumer, and increasing the diversity of fresh corn products.

‘Yongyou 988’ is a new maize variety bred by Hebi Academy of Agricultural Sciences with T1932 from European flint line as the female parent and ‘Xun 856’ as the male parent, and it was approved by the nation for Huang-Huai-Hai summer maize region in 2021. In this study, the breeding process, parent source and characteristics, yield performance, stress resistance, disease resistance and quality analysis of the variety were analyzed. The study proposed that in variety breeding, we should highlight the exploration and utilization of excellent germplasm resources, strengthen adversity selection and improve ecological adaptability of the varieties, so as to breed a new maize variety with high yield and quality, wide adaptability, density tolerance and strong stress resistance.

【Objective】The objective of this study is to perform the genome-wide identification of the maize ACO (1-aminocyclopropane- 1-carboxylate oxidase) gene family, analyze its expression patterns in different organs and developmental stages of maize, as well as in response to exogenous hormones and pathogen infection, and to lay the foundation for clarifying the function of the maize ACO gene family.【Method】Using bioinformatics methods, the ACO was identified in the genome of maize B73 inbred line, and its gene structure, protein physicochemical properties, phylogenetic relationships among family members, and conserved motifs were analyzed. The expression patterns of the ZmACO gene family were analyzed using real-time fluorescence quantitative PCR (qRT-PCR) technology.【Result】Except for ZmACO11, all members of the ZmACO family have Fe²⁺ binding sites and substrate ascorbic acid binding sites. The phylogenetic tree showed that ZmACO2 and ScACO are in the same branch and have a close genetic relationship, with a Bootstrap value of 98. The gene expression analysis indicated that ZmACO2, 5, 9, 15, 20 and 35 were actively expressed at various developmental stages and exhibited dominant expression in leaves, so the six genes mentioned above were selected for the next step of testing. Spraying ethephon resulted in fluctuations in the expression of all six genes mentioned above, the expression level of ZmACO2 was significantly affected, with a variation multiple of about 8 times. The expression levels of these six genes fluctuated within 0-24 h of ethephon treatment. But after 24 h of treatment, all gene expression levels were close to 0. After salicylic acid treatment, the expression level of ZmACO5 was significantly affected, with a variation multiple of about 2 times. The expression levels of other genes were close to 0 at 24 h after treatment. The expression levels of ZmACO9, 35 fluctuated between 3 to 12 h, and the expression levels of ZmACO2, 15, 20 showed a downward trend. In response to biological stress, the expression levels of ZmACO5, 9 showed the greatest changes after inoculation with the Setosphaeria turcica, and on the 10th day after inoculation, the expression levels of these two genes increased by 50 and 60 times, respectively, compared to the control group. After inoculation with the Cochlibolus heterostrophus, the expression level of ZmACO5 changed significantly, with a variation multiple of 40-90 times. After inoculation with Rhizoctonia solani, the expression levels of ZmACO5, 35 showed the greatest changes, reaching 200 times on the 3rd day of inoculation.【Conclusion】The expression changes of ZmACO2, 5, 20 and 35 are most active during the growth and development of maize; The application of exogenous ethephon and salicylic acid can significantly affect the expression level of ZmACO genes. The expression level of ZmACO genes significantly changes after bacterial infection in maize, which is closely related to the response to biological stress.

The performance and characteristics of the new corn hybrid ‘Zhongkeyu 505’ are reported here to provide theoretical and practical information needed for large-scale commercialization of this hybrid. ‘Zhongkeyu 505’ was developed by crossing CT1668 as female parent and CT3354 as male parent. The yield performance, agronomic traits, drought resistance, high temperature tolerance, density tolerance, grain quality, and silage forage quality were analyzed based on the multi-year and multi-location data from national and provincial trials. The results showed that the yield of this hybrid increased by 3.4% and 8% respectively on average compared with that of the two check hybrid ‘Xianyu 335’ and ‘Zhengdan 958’. The ear characters such as ear length, ear diameter, kernel number per row, grain weight per ear and grain yield were better than those of the check hybrid. The drought tolerance reached the extremely strong standard, and the high-temperature tolerance reached the medium level equivalent to that of the check ‘Zhengdan 958’. The grain test weight was 746 g/L, the crude protein, crude fatty acid, crude starch, and lysine content reached 10.1%, 3.36%, 74.26%, and 0.3% respectively. The relative stalk feed quality was better than that of ‘Xianyu 335’ and ‘Zhengdan 958’. This hybrid is an excellent one of significant commercial value. In the process of commercial breeding of maize, special attention should be paid to the factors of the market safety evaluation of new varieties, seed production yield, stem rot, ear rot, Southern and Northern leaf blight, Southern rust, suitable planting density and lodging control etc., thus establishing a breeding method combining limited backcrossing with large population adversity screening.

The purpose of this study was to investigate the effect of different culture medium components on the germination of maize pollen, in order to screen out the optimal culture medium for in vitro germination of maize pollen, and further select suitable culture media for pollen germination of different maize varieties. In this experiment, in vitro germination method was used to test different maize varieties. Single-factor experiments were conducted to compare the effects of different concentrations of sucrose, glucose, lactose, maltose, boric acid, and calcium chloride on the vitality of maize pollen, and to explore the optimal conditions for maize pollen germination. The results showed that when the culture medium components were 0.35 mol/L sucrose, 0.85% agar, 0.01% boric acid, and 0.03% calcium chloride, the germination effect of the control group was the best, reaching 51.6%. Compared with the control group, the experimental group found that this medium had significant differences in the germination of pollen of different varieties. In this study, the pollen germination rates of 8 experimental groups of maize varieties ranged from 1.8% to 21%, and this medium was most suitable for the germination of pollen of variety ‘e12’, but not suitable for the germination of variety ‘e11’. In conclusion, the optimal culture conditions conducive to in vitro germination of maize pollen were screened out, providing valuable reference and theoretical basis for the study of maize pollen germination mechanism, maize genetic breeding, and other related research areas.

【Objective】Reasonably increasing planting density combined with appropriate nitrogen (N) application rate is an important technical approach for increasing maize yield and resource use efficiency. Understanding the interactive effects of planting density and N rate on maize growth, evapotranspiration (ET) and water use efficiency (WUE) during the growing season, could provide a basis for improving its use efficiency when increasing planting density and controlling N input in maize production. 【Method】Field experiments were conducted during 2022 to 2023 in Jilin Province. Two maize cultivars, Liangyu 99 (LY99) and Demeiya 3 (DMY3), were used in this study. Three planting densities of 50 000, 70 000 and 90 000 plants/hm² and four N application rates of 0, 100, 200 and 300 kg N·hm^-2 were designed to investigate the effects of planting density and N application rate on grain yield and water productivity of different maize cultivars, as well as the dry matter (DM), soil water content, ET and WUE at various growth stages. 【Result】Planting density significantly affected DM and grain yield of maize, but the response trends varied between cultivars. Grain yields of LY99 with 70 000 plants/hm² was 11.1% and 18.3% higher than that with 50 000 and 90 000 plants/hm², respectively. The average yield of DMY3 planted with 70 000 plants/hm² and 90 000 plants/hm² was 10.5% and 9.3% higher than that of 50 000 plants/hm², respectively. Nitrogen fertilization significantly increased DM and grain yield of maize, and also showed significant interactive effects with cultivar or planting density. Compared with N0, grain yields of LY99 were increased by 38.0% to 60.7% under N1, and the yield increases for DMY3 were 24.4% to 38.2%. Notably, the yield responses to N rates were more pronounced for LY99 compared with DMY3. For both cultivars, the yield differences between low N rate and high N rate enlarged with increasing planting density, with LY99 showing a more distinct performance. The water consumption and utilization of maize plants were also significantly affected by planting density, N rate and their interaction. During the growing season, the total ET of DMY3 continually increased with increasing density, while that of LY99 showed the highest values with 70 000 plants/hm² among different densities. In each density condition, the ET of both cultivars increased with increasing N application rates. The WUE of maize plants showed complex responses to planting density and N rate at different growth stages, due to the varied annual precipitation and distribution patterns. The average increase of water productivity of LY99 under planting 50 000 and 70 000 plants/hm² was 8.6% and 10.4% compared with 90 000 plants/hm² respectively_. DMY3 had the highest water productivity when planting 70 000 plants/hm², which increased by 5.8% and 5.3% compared with 50 000 and 90 000 plants/hm², respectively. The water productivity showed different responses to N rate among the three densities. In general, the difference of nitrogen application under low density was small, but it increased significantly under medium and high density. Compared wtih DMY3, LY99 showed higher increases for water productivity when N fertilizer was applied under medium and high density conditions. The correlation analysis showed that interactive effects of planting density and N rate significantly affected maize yield and water productivity by influencing the water utilization at various growth stages. 【Conclusion】Planting density and N rate had significant interactive effects on maize yield and water utilization in the rain-fed region of Northeast China. The two maize cultivars used in this study could obtain high grain yield and water productivity under a moderately higher density of 70 000 plants/hm² combined with 200 kg N·hm^-2 rate.

To explore the natural variations in regulating the maize kernel development and to assist in the genetic improvement of maize yield traits, in this study, 150 maize inbred lines with rich genetic variations were selected as materials for investigation. Combining 34,342 SNP markers and three models, a genome-wide association analysis was conducted on five grain-related traits. The results revealed that a total of 18 independent loci were significantly associated with the target traits, with each locus accounting for 12.24% to 15.41% of the phenotypic variations. Additionally, significant epistatic interactions were identified among four pairs of SNPs associated with kernel length, collectively explaining 5.32% of the phenotypic variations. By integrating the dynamic transcriptome data of kernel development in the B73 inbred line and functional annotations of genes, 19 candidate genes were predicted and classified into four categories: 6 enzymes, 3 ribosomal proteins, 1 transcription factor, and 9 other proteins. These candidate genes provide new genetic resources for deciphering the molecular mechanisms of maize kernel development and enhancing maize kernel size and yield. Through this research, we have not only uncovered the natural variations that regulate the development of corn kernels but also provided new genetic resources for the genetic improvement of corn yield traits. These findings are expected to bring new breakthroughs in corn breeding efforts, enhance corn production, and thereby better meet human needs for food.

This paper summarized the development history of maize improvement in China since the beginning of last century,highlighting the significant achievements in the innovation and utilization of germplasms, the breeding and utilization of elite hybrids, and the research and development of modern breeding technology. The paper also analyzed and discussed the main problems and defects in maize yield and product quality, breeding techniques, and enterprise competitiveness of China’s maize industry, with some proposals for the acceleration of technological innovation and promotion of the commercialisation of GM maize in our country in order to further elevate the level of maize breeding and industrial competitiveness.

To elucidate the effects of nitrogen fertilizer application rate on sugar content and agronomic traits of sweet corn (Zea mays L. var. saccharata Bailey), a field experiment was conducted with sweet corn variety “Yuntian 8” as the material, and five treatments were set up with nitrogen fertilizer application rate of 0, 100, 200, 300 and 400 kg N/hm². The results showed that, the linear models of the relationship between nitrogen fertilizer application rate and soluble sugar content and reducing sugar content were not significant, only on the 103^rd day after sowing, the reducing sugar content decreased slightly with the increase of nitrogen fertilizer application rate. The response of ear weight to the increase of nitrogen fertilizer application rate presented an asymptotic growth model. When nitrogen application rate exceeded 100 kg N/hm², the extent of the positive response of ear weight to nitrogen application decreased dramatically. Each increment of 100 kg N/hm² decreased the ear length by 0.29 cm. The linear models of the relationships between nitrogen fertilizer application rate and ear diameter, ear row number and grain number per row were not significant. Increasing nitrogen fertilizer application rate could decrease bare tip length. Taken together, increasing nitrogen fertilizer application rate could not affect sugar content, ear diameter, ear row number and grain number per row of sweet corn, and slightly decrease ear length. However, increasing nitrogen fertilizer application rate could significantly increase ear weight and decrease bare tip length.

【Objective】 Drought is one of the serious abiotic stresses influencing maize production worldwide. Understanding the molecular mechanisms underlying drought tolerance is of great importance in maize improvement. 【Method】 In the present study, representative maize inbred lines were selected for field drought experiment and the drought tolerance was estimated based on leaf relative water content and anthesis-silking interval. Two inbred lines with contrasting drought tolerance was used for genome resequencing and transposable element insertions were identified. The DNA methylation level of leaf and root tissues under different water treatments of the two lines were measured using Whole Genome Bisulfite Sequencing (WGBS). And the gene expression profiles of these samples were detected by RNA sequencing. The integrative atlas of transposable element insertion/deletion variants, differentially methylated regions and differentially expressed genes in the two lines were constructed. In addition, the transposable element insertion/deletion variant mediated epigenetic regulation of ZCN7, which has been conferred the drought tolerance function in our previous study, was analyzed. 【Result】 The field experiment showed inbred line H082183 showed highest drought tolerance, in which the leaf relative water content and anthesis-silking interval had no significant difference between drought and well-watered treatments. While the Lü28 displayed lowest leaf relative water content and largest anthesis-silking interval under drought. Thus, these two lines were selected for further analysis. A total of 333 754 and 333 296 transposable element insertions were identified in the genome of H082183 and Lü28, respectively. And 89 954 transposable element insertions were polymorphism between two lines. The transposable element insertions, introns and promoters showed higher CG and CHG methylation level than exons and untranslated regions. Furthermore, 41 352 differentially methylated regions were identified between H082183 and Lü28. And 60% of the differentially methylated regions were located in the transposable element insertion\deletion variants and 5 kb flanking regions. The gene expression level showed negatively correlated with CG and CHG methylation. Differentially expression analysis between H082183 and Lü28 obtained 4 196 and 3 500 differentially expressed genes in leaf and root under drought, respectively. The 19.5% and 19.7% of these differentially expressed genes were located in differentially methylated regions. Three LTR transposable element insertions were identified in the 34 kb region of ZCN7 in Lü28 but absent in the genome H082183. And the DNA methylation levels of CG and CHG in this genomic region were significantly higher in Lü28 than H082183 under both drought and well-watered environments, which conferred higher ZCN7 expression in the drought tolerant line H082183. 【Conclusion】 Our results highlight the important role of interplay of transposable element insertions, DNA methylation and gene expression under drought. And gene expression regulation mechanism of ZCN7 relied on the transposable element insertion/deletion variants mediated DNA methylation was proposed.

【Objective】Northeast China is the main grain production base in China, which has been significantly affected by climate change in recent years. It was of great significance to understand the impact of normal and extreme climate states changes on crop yield in Northeast China for regional crop production and national food security.【Method】In this study, the maize in Northeast China was used as research object, and the main climate factors affecting maize yield were screened to analyze the effects of normal and extreme climate states changes on maize yield in 81 counties in Northeast China from 1980 to 2018.【Result】(1) The average temperature, growing degree-days (GDD), and heat degree-days (HDD) during the maize growth period showed an increasing trend, and the rising rates were 0.34 ℃·(10 a)^-1, 47.07 ℃·d·(10 a)^-1, and 5.15 ℃·d·(10 a)^-1, respectively. The precipitation showed a decreasing trend, with the rate of 7.0 mm·(10 a)^-1; the average temperature, GDD, and HDD increased from northeast to southwest, while the precipitation increased from northwest to southeast. (2) The meteorological yield of maize in Northeast China showed an increasing trend from 1980 to 1999, with a rate of 80.93 kg·hm^-2·a^-1, while it showed a decreasing trend of 46.25 kg·hm^-2·a^-1 from 2000 to 2018. In terms of spatial distribution, it showed an increasing trend from the middle to the surrounding areas. The area with high yield was concentrated in the eastern part of Heilongjiang. The change of Liaoning was the most stable, and the fluctuation range was stable in the middle area. (3) By the multiple linear regression model, HDD contributed the most to meteorological yield from 1980 to 2018, and the effect was negative, which meant extreme high temperature had the greatest impact on maize yield in Northeast China and caused maize yield reduction; GDD had a positive effect, that is, the average temperature increased maize yield, and the greater GDD, the more yield increased; the precipitation had a negative effect; the interaction between temperature and precipitation had a positive impact on maize yield in Northeast China.【Conclusion】Normal and extreme climate states changes and its impact on maize meteorological yield in Northeast China from 1980 to 2018 were as follow: the normal and extreme temperature showed an overall increasing trend, while the normal precipitation showed a decreasing trend. Extreme high temperatures and normal precipitation led to a decrease in maize yield, but the average temperature increased maize yield, and the extreme high temperature had the greatest impact. In the future, it was necessary to make full use of the average temperature state and minimize the harm caused by extreme high temperature to ensure a high-stable maize production.

To study the response of maize population dry matter, yield, nutrient absorption and transport to potassium, a field experiment was conducted in Pingjibao, Yinchuan City, Ningxia from 2018 to 2019, with 6 potassium fertilizer dosages of 0, 60, 120, 180, 240 and 300 kg/hm². The results showed that potassium application significantly improved the dry matter accumulation, potassium absorption, transportation and utilization efficiency of corn. The best potassium application rate was 180 kg/hm², and the dry matter accumulation in the mature stage increased by 3.04% to 13.80% compared to the control, while the potassium accumulation in the ear increased by 32.17% to 42.57% compared to the control. Under potassium application, the potassium transport amount increased by 20.28%-68.73%, the potassium transport rate increased by 10.16%-30.37%, and the contribution rate of transported nutrients to grains increased by 20.40%-67.71%. Compared with other potassium application treatments, the potassium absorption and utilization efficiency of 180 kg/hm² increased by 20.09%-247.97%, the potassium agronomic utilization efficiency increased by 37.47%-221.27%, and the yield increased by 6.99%-18.14%. Taking into account factors such as corn yield, nutrient accumulation and transportation, and fertilizer utilization, the potassium application rate of 180 kg/hm² was more suitable under the experimental conditions

【Objective】 Maize stalk rot is one of the common and most devastating diseases in major maize production areas in China. Under natural conditions, maize stalk rot is mostly caused by the synergistic infection of various pathogens. The purpose of this study was to screen elite maize germplasms resistant to the synergistic infection with F. graminearum and F. verticillioides. Meanwhile, QTN associated with resistance to the infection by synergistic infection of two Fusarium species and the candidate resistance genes were identified, which will provide gene resources and theoretical reference for molecular breeding of maize variety resistant to synergistic infection of different pathogens.【Method】 Using a maize natural population as experimental materials, the maize stalk rot phenotypes were investigated upon simultaneous infection with F. graminearum and F. verticillioides. Furthermore, GWAS analysis was conducted to identify significant resistance SNP and to predict candidate genes for stalk rot resistance.【Result】 Through the phenotypic analysis of stalk rot caused by synergistic infection under both field and laboratory conditions, it was found that inbred lines from different sources and subgroups showed significant phenotypic variation. More specifically, the field assay results showed that the inbred lines collected from China were more resistant and that from USA were more susceptible to synergistic infection. Moreover, the inbred lines of tropical and subtropical subgroup were more resistant, whereas the inbred lines of Mixed subgroup more susceptible. The seedling assay results under laboratory condition showed that the lines collected from USA were more resistant, whereas that from CIMMYT were more susceptible. The lines of SS subgroup were more resistant, and that of Mixed subgroup were more susceptible. By integrating field and laboratory phenotypic data, 29 and 16 lines with higher levels of resistance to synergistic infection were screened out respectively, and 6 resistant lines were identified under both conditions. Moreover, based on the field phenotype GWAS, 18 QTNs associated with the resistance were identified, and 93 candidate genes associated with stalk rot resistance to synergistic infection were mined. Among these candidate genes, four genes showed haplotype variation, whose expression levels were up-regulated in disease-resistant lines.【Conclusion】 Using the natural population of maize with great diversity in genetic background, 6 resistant lines to the synergistic infection with Fusarium spp. were identified under two conditions, which can be used as potential germplasm resources for maize stalk rot resistance in the future. Four candidate genes that might be involved in the resistance to synergistic infection were identified by GWAS, which will provide genetic resources for the breeding maize varieties with enhanced resistance to stalk rot caused by F. graminearum and F. verticillioides.

【Objective】 The lack of soil nitrogen impacts the yield and quality of maize, which is a major problem of maize production in China. ZmCCT10 encodes the transcription factor, which is pleiotropic. ZmCCT10 is a very important co-factor regulating the growth, development and responding to abiotic stress of maize. The molecular mechanism of maize tolerance to low nitrogen is the basis for breeding maize varieties with low nitrogen tolerance and high nitrogen efficiency. 【Method】 In this study, we compared the traits those relate to low-nitrogen tolerance, expression pattern of ZmCCT10 and transcriptome results of ZmCCT10 near-isogenic lines under low-nitrogen stress and complete nutrient conditions. To analysis the characteristics of ZmCCT10 in response to low-nitrogen stress and the molecular mechanisms involved in low-nitrogen tolerance were explored. 【Result】 This study indicated that different alleles of ZmCCT10 showed significant differences in root length traits, biomass and nitrogen physiological traits under low nitrogen stress. The Y331-ΔTE haplotype without transposon insertion of ZmCCT10 had significantly longer total root length, main radicle length and lateral root length than Y331 after low nitrogen stress. What is more, root dry weight, shoot dry weight, nitrogen accumulation and nitrate reductase activity were also significantly higher than Y331. The expression levels of ZmCCT10 in roots and leaves were significantly higher than those in the control treatment. The expression level of ZmCCT10 in roots reached a peak at 3 hours after stress treatment. In leaves, the expression of ZmCCT10 continued to increase and peaked 6 hours after stress treatment. Root samples were collected under 0.04 mmol·L^-1 low nitrogen stress after 3h for transcriptome sequencing. The correlation coefficients between biological replicates are more than 0.9. GO enrichment analysis showed that the expression levels of amine synthesis process and cellular nitrogen compound catabolic process were significantly different in near-isogenic lines after low nitrogen stress. Combined with the amount and expression pattern of differential genes, ZmCCT10-regulated candidate genes involved in low-nitrogen tolerance were selected. qRT-PCR confirmed that the expression levels of ZmMPK5, ZmNS2 and other genes were significantly different after stress in near-isogenic lines. 【Conclusion】 ZmCCT10 is a candidate gene involved in low nitrogen tolerance in maize and it participates in the low-nitrogen tolerance response of maize as transcriptional regulation.

In order to screen out the maize varieties with low-nitrogen tolerance, and provide the technologies for identifying and screening low-nitrogen-resistant corn varieties, 36 corn cross combinations were used as test materials, the phenotypic value of genotypic agronomic traits was determined under the condition that the amount of nitrogen used was reduced by 70% compared to the normal amount of nitrogen applied. Based on the phenotypic value, the comprehensive coefficient of low nitrogen stress was calculated, and then the genotype's ability to low nitrogen resistance was evaluated. The results showed that there were significant or very significant differences in the performance of most agronomic traits among different genotypes under low nitrogen stress. The comprehensive coefficient of low nitrogen stress varied greatly among 36 genotypes, with a maximum value of 1.0319, a minimum value of -0.1139, and an average of 0.4506. There were 6 and 4 genotypes with very significantly and significantly greater coefficients than the average, respectively; 16 genotypes had no significantly different from the average; there were 2 and 8 genotypes with significantly and very significantly smaller coefficients than the average, respectively. Genotypes with extremely significant and significantly greater coefficients than the average were rated as varieties with strong and stronger low-nitrogen resistances. Vigorous growth, higher plants, and wide ear leaves could be used as important characteristics for selecting low-nitrogen-resistant varieties under low-nitrogen stress.