Ezatollah Farshadfar and Parvin Elyasi
In order to study the response of twenty different bread wheat (T. aestivum L.) landraces to drought stress, an experiment was conducted in a randomized complete block design with three replications under rainfed and irrigated conditions during 2010-2011 cropping season. Significant positive correlation was found between grain yield in the stress condition (Ys) with indices stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP), yield index (YI), yield stability index (YSI), drought response index (DRI), drought resistance index (DI), relative drought index (RDI), abiotic tolerance index (ATI), stress non-stress production index (SNPI) and modified stress tolerance index (MSTI). Significant negative correlation was found between Ys with RDY and SSI indices. Principal component analysis (PCA), indicated that first and second PCA accounted for 98.87% of variations among the indices. Biplot diagram indicated that the most suitable indices for screening drought tolerant genotypes were GMP, MP, STI, K1STI, K2STI, YI, DRI, DI, SNPI, RDI and YSI. Screening drought tolerant genotypes using ranking method discriminated genotypes (18), (10), (2) and (5) as the most drought tolerant. Therefore they are recommended to be used as parents for genetic analysis, gene mapping and improvement of drought tolerance in common wheat.