Genome-wide Association Analysis Of Maize Traits At Seedling Stage Under Low Phosphorus Condition

Phosphorus (P) deficiency is one of the major limiting factors in maize production. Molecular breeding is an effective way to improve maize resist low phosphorus condition and reduce the yield losses caused by low phosphorus. In recent years, many researches indicated that whole genomics which was used to gene association analysis had been an effective method for low phosphorus resistance gene isolation and identification.In our research, traits of 456 maize inbreds were used to evaluate phenotypic and genetic at the seedling stage, and use genome-wide association analysis to find candidate genes response to low phosphorus condition. Results showed below.1. All 456 maize inbreds were cultivated in river sand under non-applied phosphorus (NAP) and applied phosphorus (AP) conditions. Analysis of variance revealed significant genetic variation among genotypes for all tested traits. Medium-to-high heritability estimates were obtained for most traits. Dry weight (DW) was highly inheritable while the widely used root/shoot ratio (R/S) had only an intermediate level of heritability. Based on the synthetic index (SI), the all tested inbreds were classified into three groups (group 1, group 2 and group 3) representing low, moderate and high tolerance to low P stress. The allometric coefficient (k) were low in group 1, moderate in group 2, and high in group 3 under NAP condition, but the k values were almost identical among the three groups under AP condition. Regression model built based on selection criteria for low P tolerance explained 67.8% and 76.8% of variation for DW under NAP and AP conditions, respectively. Using joint low P tolerance index (LPTI) for DW and SI as selection criterion, 23 and 109 maize inbreds were identified as high and low P tolerance germplasms, respectively, which could be further used for genetic improvement of low P tolerance.2. All the genotypes were identified use Illumina SNP50,50761 high quality and diversity SNP markers were obtained in this research, which could be used in further genome-wide association analysis. The results showed that under the significance level of P>4.71, there are 44 SNP markers associated with 15 traits under NAP condition, and 62 SNP markers associated with 16 traits under AP condition. The significant associated SNP markers can explain the phenotypic variation of 4.87-7.71%.3. Classified the gene after blasting in the database of NCBI and MaizeGDB. According to the analysis of gene function, four candidate genes were found to have important function in the low phosphorus resistance pathway. Including auxin response factor, AUX/IAA protein, ADP-ribosylation factor and MYB family transcription factor.