Determination And Genome-wide Association Analysis For Kernel Test Weight Of 517 Maize Germplasms

Maize(Zea mays L.)is the largest grain crop with the largest planting area in China,playing a crucial role in ensuring food security in China.China has abundant local maize germplasm resources,but their development and utilization are relatively limited.Therefore,precise identification and evaluation of them is particularly important and urgent.The test weight is an important evaluation index for the quality grade of corn,and a one vote veto system is implemented in the approval standards for ordinary corn varieties.Therefore,conducting research on the test weight of maize germplasm grains is of great significance for improving the quality of maize in China.517 maize germplasms were used as associated populations,propagates and purifies them at 3 experimental sites(Lin’an,Dongyang,Ledong),identifies and analyzes them,and selects high capacity and weight maize germplasms;Using SNP markers to conduct genome-wide association study,mining candidate genes related to test weight,and providing excellent germplasm or genes for new high-quality maize varieties in China.The main results are as follows:1.Grain test weight is influenced by environment,variety,and their interaction.Analysis found that environment,variety type,and their interaction all have a significant impact on grain test weight,indicating that grain test weight is a complex quantitative trait.In addition,a total of212 first level germplasm with a population test weight ≥ 720 g/L were selected,including 161 ordinary maize,3 burst maize,33 backbone inbred lines,12 glutinous maize,and 2 sweet maize.From the three experimental sites,the overall average value of Ledong experimental site is the highest,with first-class germplasm accounting for 37.78%.A warm,humid,and well lit environment is a favorable condition for cultivating high capacity and weight maize.2.8 high test weight germplasm were selected from 517 germplasm.The maximum unit weight values at Dongyang,Lin’an,and Ledong experimental sites were 904 g/L,921.88 g/L,and840 g/L,respectively,which were 295.72 g/L,248.41 g/L,and 143.13 g/L higher than the corresponding population average values.Among them,eight high test weight germplasm resources,including "Autumn Corn","8902","Dajindi","Zheng30","Pan’an Baizi","Mountain Maize White Seed","CML115",and "Yellow White Class Explosion",can be used as ideal materials for variety breeding.In addition,the test weight of "Xiaohuangnuo","Zheng30",and "Mountain Maize White Seed" showed excellent performance at different experimental points,and can be regarded as stable high test weight germplasm that is less affected by the environment.From the perspective of variety types,sweet corn has a low test weight value while burst corn has a high test weight value.3.Excavated 14 candidate genes related to test weight traits.146 and 261 significant SNP loci were screened in Dongyang and Ledong,respectively,with an average phenotype interpretation rate of 12.03% and 12.56%,respectively.Among them,site S6＿10538863,S4＿89385496 explained a relatively high phenotypic variation rate,with PVE of 39% and 20.09%,respectively.No significant loci were found in Lin’an.There are 42 overlapping sites between Dongyang and Ledong,distributed on chromosomes 3,4,7,and 8.Excavate 14 candidate genes near overlapping sites,which are related to various functions such as organic matter accumulation,biological metabolism,signal transduction,and stress.Multiple candidate genes have been reported.In summary,this study used 517 maize germplasm as the research population,and conducted heavy purification and identification analysis at three experimental sites in Lin’an,Dongyang,and Ledong.A batch of germplasm with a unit weight≥720 g/L,such as "Autumn Corn","8902",and "Dadijin",as well as 8 high-quality breeding materials with a high unit weight(≥840 g/L)were selected;Two high PVE value loci were screened through GWAS,and 14 candidate genes related to test weight traits were identified.These genes are related to organic matter accumulation,biological metabolism,signal transduction,stress and other functions.The research results not only help promote high-quality high-capacity maize varieties in actual production,but also provide candidate gene ideas and excellent germplasm for future exploration of new high-capacity maize varieties.