Evaluation of Bread Wheat Genotypes for Drought Tolerance using Agro-Physiological Traits

This research was investigated to study the agronomic and physiological characteristics of 20 bread wheat genotypes under both rainfed (stress) and irrigated (non-stress) conditions in the filed (RCBD) and laboratory (CRD) with three replications in Sararood Dryland Agricultural Research Station، Kermanshah، Iran، in 2004-05 cropping season. Genotypes were evaluated for physiological and agronomic traits in the both field and laboratory conditions. The genotypes differed significantly for the measured traits. Genotype No. 17 (Marvdasht) with the highest yield under normal condition had the highest stress tolerance index (STI) and tolerance index (TOL)، whereas genotype No. 20 (Sardari) with the highest yield under rainfed had the lowest TOL and moderate STI. The results of regression analysis indicated that traits of Pro، Chl-a، DH، PedL، PH and TKW were accounted for 60% of total variation of grain yield under rainfed condition.. Based on results of correlation analysis، the laboratory traits were as a good alternative for most of field traits. Therefore، use of them for some selections in filed can be suggested. According to principal component analysis (PCA) and biplot analysis، the genotypes No. 11، 9 and 10 with relatively high yield in the both conditions had high proline content and high TKW and the highest germination stress index (GSI) and promptness index (PI). Genotype No. 17 with the highest yielding production under normal condition was characterized as genotype with the highest values for STI، chlorophyll fluorescence، cellular membrane stability and Chl-a and Chl-b. STI was positively (P<0. 01) associated with yields under both stress and non-stress conditions، thus can be regarded as suitable index for screening drought tolerant genotypes.