Physiological and yield responses of bread wheat (triticum aestivum l.) genotypes to pre-and post-flowering water stress

Abstract

Screening genotypes using physiological and agronomic traits and stress tolerance indices that are considered as putative selection criteria is crucial in order to develop resilient genotypes for drought prone environments. Thus, the present study examined the effect of different moisture regimes based on Total Available Water (TAW) on yield and physiological traits of bread wheat (Tritium aestivum L.) genotypes. A factorial combination of three moisture regimes (optimum maintained at 80% of TAW, pre-and post-flowering water stress each of them maintained at 30% of TAW) and eight bread wheat genotypes were tested in a completely randomized design (CRD) with three replications under greenhouse condition. The analysis of variance revealed highly significant difference among genotypes for most physiological and yield and yield related attributes studied, showing the existence of genetic variability which could be used to breed for tolerance to moisture stress. The genotypes × moisture regimes interaction was also significant for most of the characters indicating the inconsistency of the performances of genotypes across moisture regimes and the need for selection of bread wheat genotypes that are specifically adapted to a particular moisture regime. Higher grain yields were harvested from genotypes B, C and E with an advantage of 65, 54 and 36%, respectively over the tolerant check at pre-flowering water stress regime. On the other hand, under post-flowering water stress regime genotypes A and D showed significantly superior performance over the tolerant check, with 85 and 72% increments, respectively. In addition, GEE biplot allowed the winning genotypes to be distinguished for each moisture regime mega environment. Accordingly, genotypes, B, C and E were identified as drought tolerant and suitable to pre-flowering water stress mega environment whereas genotypes, A and D were ideal genotypes to post-flowering water stress mega environment. Moreover, genotype H was the most stable genotype across all moisture regimes while genotypes F and G thrived best under optimal condition. Besides, results of correlation analysis between stress tolerance indices and grain yield in pre-flowering water stress condition revealed that TOL, HM, SSI, DRI, YSI and YI showed a high power of discrimination among genotypes. Also, TOL, MPI, GMP, HM, STI, SSI, DRI, YSI and YI were the best indices for identifying high yielding genotypes at post-flowering water stress condition. Hence, these indices could be used as selection criteria for screening genotypes under different moisture stress regimes. Principal component analysis (PCA) showed that 98 and 95% of the total variation was explained by the first six and four PCs under pre-and post-flowering water stress conditions, respectively. Thus, traits included in the first PCs particularly traits with higher vector loading scores are pertinent in screening bread wheat genotypes at each water stress regimes. Therefore, based on evaluations, it could be recommended that genotypes A, B, C, D and E along with tolerant check should be promoted for further testing under field conditions both to confirm the results and to put them in the pipe line for release.