STRESS SELECTION INDICES AN ACCEPTABLE TOOL TO SCREEN SUPERIOR WHEAT GENOTYPES UNDER IRRIGATED AND RAIN-FED CONDITIONS

Abstract

The climate is changing day by day and water scarcity has developed a milieu for the breeder to think accordingly. Twenty-four advanced wheat lines along with four prominent check cultivars were evaluated independently in irrigated (IRE) and rain-fed environments (RFE) for yield related traits at Khyber Pakhtunkhwa, Pakistan during 2010-11, using randomized complete block design with three replications under each test environment. Analysis of variance across the two environments exhibited highly significant variation (p≤0.01) among the genotypes for yield and associated traits. Differences among the two test environments (E) were significant for tillers m-2, 1000-grain weight and harvest index. Genotype × environment interaction (G×E) effects were significant only for 1000-grain weight and grain yield. There was general reduction in 1000-grain weight, biological yield and grain yield of all genotypes under RFE as compared to IRE. Magnitude of heritabilities estimates were greater for tillers m-2, spikelets spike-1 and grains spike-1 under IRE than RFE. Heritabilities were greater in RFE than IRE for spike length (0.31 vs 0.26), biological yield (0.80 vs 0.22), grain yield (0.94 vs 0.20) and harvest index (0.41 and 0.39). Relative high expected selection response was recorded for all characters under IRE except spike length, grains spike-1 and grain yield. In IRE, highest grain yield was produced by genotypes BRF-7 (5123 kg ha-1), B-VI(N)16 (5111 kg ha-1), B-IV(N)1 (5086 kg ha-1) and B-VI(N)5 (5049 kg ha-1), while genotypes B-VI(N)5 (4649 kg ha-1), B-IV(N)1 (4595 kg ha-1), BRF-7 (4486 kg ha-1) and B-IV(N)16 (4462 kg ha-1) were high yielding under RFE. Prominent stress selection indices used in the experiments were mean productivity (MP), tolerance (TOL), stress tolerance index (STI), trait index (TI) and trait stability index (TSI). MP and STI were the efficient and reliable selection indices in both environments (IRE & RFE). MP, TOL and STI had strong positive relationship with tillers m-2, spikelets spike-1, 1000- grain weight, biological yield and grain yield under IRE. Mean stress indices showed that the top ranking genotypes for MP and STI were B-VI(N)6, BRF-7, B-VI(N)5 and B-II(N)3, reflected their superior performance across both the conditions.