Genetic variability of some physiological and yield-related traits in bread wheat recombinant inbred line populations under heat stress Conditions

A population consisted of 169 recombinant inbred lines (RILs) derived from direct and reciprocal crosses between Seri M82 and Babax was grown at the Gezira Research Station Farm (GRSF), Wad Medani, and Dongola Research Farm (DRF), Dongola, during two growing seasons 2008/09 and 2009/10 (DON08-DON09), (MED08-DON09). The objectives were to (i) evaluate the genetic variability for heat stress adaptation in the Seri/Babax population in two contrasting environments in terms of phenological, physiological and yield related attributes, (ii) identify the traits best associated with yield under heat stress conditions, (iii) assess the feasibility of utilising secondary selection criteria to identify high-yielding genotypes, and (iv) assess genotype x environment interactive effects on wheat performance. The experiment was arranged in an alpha lattice design with two replications. Results indicated a wide range of genetic variability among the RILs at all environments. For example, the grain yield at DRF ranged from 4375 to 8675 kg/ha and from 2079 to 4712 kg/ha, in the 1st and 2nd seasons, respectively. The range in grain yield at GRF was from 1677 to 4275 kg/ha and from 1250 to 3091 kg/ha, in the 1st and 2nd seasons, respectively. Combines analysis of variance revealed highly significant effects of environments, genotypes and genotype x environment interactions for most studied traits. Grain yield significantly and positively correlated with biomass, harvest index, grain spikE-1, days to heading and days to maturity at both locations, while it was significantly and negatively correlated with canopy temperature during grain filling at both locations. AMMI analysis with the first principal component (PCAl) was highly significant, while the second principal component (PCA2) was not significant. Based on AMMI analysis, the best four genotypes at each environment were identified to be entries No. 33, 27, 20, 42 and 6, 134, 26, 18 at DON09 and DONI0, respectively, and entries No.6, 134, 26, 142 and 140, 109, 29, 155 at MED09 and MED10, respectively. Most of these entries showed high biomass, late maturity, long grain filling period, high number of spikes mE-2, high leaf chlorophyll content and cooler canopy temperature. The GGE biplots explained about 71% of G and GE variation, of which 51.3 and 19.7% was accounted for PCl and PC2, respectively. The GGE biplot showed that the four environments were separated into three groups. The GGE biplot view also provided information on the performance of the genotypes. Entry 33 was the winning genotype in the 1st group, entry 134 in the 2nd group and entry 6 in the 3rd group. Based on significant correlations with grain yield, high biomass, late maturity, long grain filling period, cooler canopy temperature, and high numbers of spikes mE-2 can be used as potential selection criteria for high grain yield under high temperature conditions