Identification of new microsatellite marker linked to the grain filling rate as indicator for heat tolerance genes in F2 wheat population

The objective of this study was to estimate inheritance of the grain filling rate as indicator for heat tolerant genes. The minimum number of genes for the trait in bread wheat was also assessed by combining quantitative genetic estimates and SSR marker analyses. Two cultivars, Debra (heat-tolerant) and Yecora Rojo (heat-sensitive) crossed and F1 and F2 populations generated. The parents, F1 and 162 F2 plants were planted in winter season 2009 to evaluate heat tolerance during the grain-filling period. The sowing date in the present investigation represents the heat stress conditions in Saudi Arabia. The minimum number of genes or factors controlling heat tolerance was estimated (1.5) and the broad sense heritability was estimated as 47.7 %. The results revealed that three SSR markers; Xgwm132, Xgwm577 and Xgwm617 were linked to grain filling rate (GFR) by quantitative trait loci (QTL) analysis of the F2 population. The results showed that regression analysis for the relationship between the three markers (Xgwm132, Xgwm577 and Xgwm617) and the phenotypes of F2 plants were highly significant and the coefficients of determination (R) were 0.07, 0.25 and 0.03, respectively. This indicates that these three markers were associated with the grain filling rate as indicator for heat tolerant genes. The adjusted R values suggested that the Xgwm132, Xgwm577 and Xgwm617 accounted for 7%, 25% and 3% of the total phenotypic variation of heat tolerance in the F2 population, respectively. The results demonstrated that SSR markers, combined with bulked segregant analysis, could be used to identify molecular markers linked to the grain filling rate as indicator for heat tolerance in wheat.