Tolerance and stability studies on durum wheat under drought and heat stress conditions

This study was conducted to determine the stability of grain yield and test weight, and the susceptibility index (S) of durum wheat under stress condi tions. The genotypes were grown in replicated trials at Ceylanpinar State F arm in Southeast Anatolia under supplementary irrigation between 1992 and 1 994, and in lowland and upland conditions in the Mediterranean region of Ad ana under rainfed conditions between 1992 and 1995. Stability parameters we re estimated from the regression analysis as linear regression coefficient (bi) and coefficient of determination (r(2)), and from Kang's yield stabili ty index (Ysi). Stress tolerances were estimated using stress susceptibilit y index (S). Genotypes evaluated in this study exhibited a wide range of stress toleranc e and adaptation to stressful environments. Considerable variation in the S values of certain genotypes occurred between stress environments in this r esearch. Stress susceptibility index (S) ranged from 0.835 to 1.243, and fr om 0.588 to 1.513 for grain yield and test weight, respectively. Test weigh t index showed greater variation than grain yield index. Differential varia tion among genotypes for S probably depends on heat stress and drought stre ss which occurred during grain filling periods. Regression coefficients ran ged from 0.674 to 1.306 and from 0.574 to 1.424 for grain yield and test we ight, respectively. Kang's yield stability statistic index ranged from -4 t o +27 and from -6 to +28 for grain yield and test weight, respectively. Stable lines, stress-tolerant and susceptible lines were identified for use in the evaluation of stress tolerance screening techniques and of stabilit y parameters. Based on these findings, selected lines have been chosen as v aluable initial material in durum wheat breeding for stress environments.