Germplasm Screening And Genome-wide Association Analysis For Chilling Tolerance During Germination And Budding Stage In Maize

Chilling stress has become one of major limiting abiotic stress factors of maize production in Northeast region.It is a most cost-effective way to breed maize germplasm tolerant to chilling.Mining of chilling tolerance genes is an important prerequisite for the cultivation of germplasm tolerant to chilling.The establishment of a highly-accurate and stable system for the identification and evaluation of chilling tolerance is an important condition for the breeding.With the development of molecular biology and its wide application in agriculture,it greatly promoted the development of functional markers related to chilling tolerance,and further promoted the process of germplasm discovery and variety cultivation tolerant to chilling.In this study,multiple indexes related to chilling tolerance were measured and principal component analysis,regression analysis and cluster analysis were used to comprehensively evaluate the chilling tolerance at the germination and budding stages.Genome-wide association analysis was conducted by combining the high-throughput genotypes of 70 inbred lines with the phenotypes of chilling tolerance evaluation.The significantly associated SNPs for chilling tolerance traits were screened.The major results were as follows:1.The comprehensive evaluation results of chilling tolerance indicated that at the germination stage,six single indexes for maize hybrids and inbred lines were synthesized into two independent comprehensive indexes under 10? through principal component analysis.65 hybrids were divided into 5 groups by systematic clustering,in which the materials with excellent cold resistance,strong cold resistance,middle cold resistance,weak cold resistance and very weak cold resistance were 14,24,16,7 and 4,respectively.The 70 inbred lines were also divided into 5 groups by systematic clustering,in which the materials with excellent cold resistance,strong cold resistance,middle cold resistance,weak cold resistance and very weak cold resistance were 9,26,19,9 and 7,respectively.2.The comprehensive evaluation results of chilling tolerance indicated that at the budding stage,inbred lines and hybrids were all divided into 5 levels under 2“C based on the survival rate.The hybrids with excellent cold resistance,strong cold resistance,middle cold resistance,weak cold resistance and very weak cold resistance were 3,3,7,32 and 20,respectively.The inbred lines with excellent cold resistance,strong cold resistance,middle cold resistance,weak cold resistance and very weak cold resistance were 1,4,3,37 and 25,respectively.3.The results of genome-wide association analysis indicated that genome-wide association analysis has been performed between 41,372 SNPs and valuation value of chilling tolerance in 70 maize inbred lines by mixed linear model.13 SNPs significantly associated with chilling tolerance at germination stage were detected,which were located on chromosome 1,3,4,5,6,8 and 10.The single SNP could explain 9.30%-25.97%variation of phenotype.6 SNPs significantly associated with chilling tolerance at budding stage were detected,which were located on chromosome 1,2,7,8,and 9.The single SNP could explain 5.66%-28.39%variation of phenotype.