Genome Wide Association Study of Yield and Yield-Related Traits in Elite Spring Bread Wheat Genotypes Grown under High Temperature Environment in Sudan

Genetic improvement of wheat for heat tolerance is the main breeding objective in Sudan as it is the principal limiting factor for wheat production. To this end, the availability of wheat genetic diversity is key for success. Genetic diversities and genome-wide association studies were conducted to parse the complex genetic composition of yield-related traits of 250 bread wheat genotypes which were selected from ICARDA’s advanced materials. The genotypes were evaluated under heat stress environment for two seasons (2016/17 and 2017/18) in two sowing dates (optimum and late) at the Gezira Research Farm (GRF), of the Agricultural Research Corporation (ARC), Wad Medani, Sudan. Yield levels ranged from 4016 - 5120 kg/ha for optimum and late sowing dates respectively in the first season and from 5386 - 3926 kg/ha for optimum and late sowing dates respectively in the second season. The top 20 genotypes were better than the best check in the two seasons except, Imam which ranked number 18 in the second season. Two genotypes, genotypes 27 and 37, produced high grain yield in both seasons. Wide ranges of variations among genotypes were found for yield and yield-related traits, including days to heading and maturity, plant height, number of seeds/spike, 1000 seed weight, biomass and harvest index. Genome wide association analyses were performed using 15 kSNPmarkers and the phenotypic data. A total of 282, 355 and 475 significant (P served in the first season, second season and across seasons, respectively. Markers (6B/Kukri_ c27662, 6B/.BobWhite_c23771_525, 6B/Excalibur_c32219_491, 6B/RAC875_c31299_13021302, 6B/BS00046264_51,6A/wsnp_Ex_rep_c69373_68312188, 6A/Tdurum contig12123_1650, 6BKukri_c27662_675 and 6A/BobWhite_c15802_72) on chromosomes 6B and 6A for grain yield were highly significantly associated and stable in every season and across seasons. Highly significant Marker-traits associations (MTAs) were observed for many traits including days to heading and maturity, plant height, number of seeds/spike, 1000 seed weight, biomass and harvest index. The currently identified MTAs should be further validated using other elite sets of genotypes so that they can be used for MAS in the breeding program. The high yielding and heat tolerant genotypes identified in this study will be evaluated across key locations in Sudan for potential release in Sudan. Furthermore, they will be used as parents in the breeding program for heat tolerance.