DROUGHT TOLERANCE INDICES AND THEIR CORRELATION WITH YIELD IN EXOTIC WHEAT GENOTYPES

Performance of nineteen exotic genotypes along with local check variety was studied during 2009-10 at Wheat Research Institute, AARI, Faisalabad, Pakistan. The experiment was conducted under two field conditions i.e., stress and irrigated conditions. In case of water stress experiment, only soaking irrigation was applied for seed bed preparation and no further irrigation was applied up to maturity. While, four irrigations were applied at critical growth stages to the second experiment (irrigated). At maturity, grain yield was recorded in both experiments (stress Y-s and irrigated Y-p). From grain yield data, some drought tolerance/resistance indices such as tolerance index (TOL), mean productivity (MP), harmonic mean (HM), stress susceptibility index (SSI), geometric mean productivity (GMP), stress tolerance index (STI), yield index (YI), yield stability index (YSI) and modified stress tolerance index (k(1)STI & k(2)STI) were calculated. Genotypic correlation, genetic components and heritability were also calculated for grain yield and all indices. Significant differences among genotypes were observed for Y-p, Y-s and all other drought tolerance indices. Moderate to high heritability and genetic advance were observed for Y-p, Y-s and all drought tolerance indices. Grain yield under irrigated environment (Y-p) was positively and significantly correlated with MP, HM, GMP, STI and k(1)STI. Similarly, positive and significant association has also been observed between grain yield under stress condition (Y-s) and MP, HM, GMP, STI, YI and k(2)STI so they were the better predictor of potential yield Y-p and Y-s than TOL, SSI and YSI. According to Fernandez model; genotypes No. 2, 4, 6, 7, 9 and 13 have uniform superiority under both conditions (stress and irrigated). Genotypes No. 1, 11, 15, 16, 17, 18 and 19 were recommended for irrigated conditions. Genotypes No. 3 and 5 were identified suitable for stress conditions. While genotypes No. 8, 10, 12, 14 and 20 performed poorly under either environments (stress and irrigated).