Genome Wide Association Analysis for Uniform Coleoptiles Emergence and Early Seedling Growth in Rice

Early seedling vigour (ESV) is a complex trait in rice. Detection of QTLs/genes controlling these traits can help us in enhancing the yield potential in rice varieties. Association mapping is a technique based on the principle of linkage disequilibrium that is used to find genes or quantitative trait loci (QTL) underlying the complex traits. In this study of haplotype breeding 281 rice genotypes were taken. ANOVA analysis showed P- value for traits and genotypes was found significant. Similarly, P-value for interaction between the traits and genotypes was also found to be highly significant (1.8663*10-208). Further, mean germination data positively correlated with mean shoot length, mean leaf number, mean culm diameter, mean shoot dry weight, and mean shoot area of 21st day among the 281 genotypes. Among the 281 number of genotypes, 111 genotypes are found to be in PCA1 and 170 genotypes are found to be in PCA2 based on the phenotypic analysis. PCA1 component constituted 29.93% and PCA2 constituted the 13.68% of total variation in the analysis. Besides, whole genome phylogenetic analysis showed three major groups of which Group 1 consists of 215 genotypes, group 2 consists of 38 genotypes and group 3 consists of 28 genotypes respectively. Especially, both the subgroups II and III comprised of the unique genotypes from the indica and aus subpopulations of rice. In this analysis, 16 significant associations (LOD Score >7) for different traits were identified using the three different models (MLM, farmCPU, and blink) for GWAS studies Especially, one major QTL was identified for the mean coleoptiles’ emergence for 10 DAS on 11th chromosome (18983591) which explained 49% of the phenotypic variance. Additionally, another major QTL contributing to the shoot length variation of 29.75% was identified in the Chr02 (32954393) for shoot length trait on 28 DAS. A candidate gene namely Os02g0778400 UMP/CMP kinase A/adenylate kinase (LOC_Os02g53790) was located in the significant SNP region of the GWAS analysis. Further characterization of this gene would assist in elucidation of the mechanism regulating the early seedling length in rice under direct seeded rice.