Assessment of Durum Wheat Genotypes by Drought Tolerance Indices under Drought and Normal Condition

Background: Drought is a major problem reducing agronomic crop production worldwide. Increasing the genetic potential of yield in water deficit condition is one of the major objectives of durum wheat breeding programs in world. Methods: In this study, 20 genotypes of durum wheat (Triticum durum Desf.) were assessed in both water-stressed and well-watered environments for 2 years i.e. 2017-18 to 2018-19 rabi season. In each environment, each genotype was sown in four rows of 2.5-meter length and 20 cm apart using a randomized complete block design with two replications. Eight drought tolerance indices were applied based on grain yield in drought stress (Ys) and normal irrigation (Yp) conditions. Highly significant differences for yield (Yp and Ys) and all drought tolerance indices were observed indicating differences in genotypes for genes controlling yield and drought tolerance indices. Result: High yield values in non-stress and stress environments were exhibited by genotypes GW 1339 (8254.29 kg ha-1, 2970.83 kg ha-1) followed by GW 2017-864 (7512.50 kg ha-1 2756.25 kg ha-1) and HI 8737(7186.47 kg ha-1, 2845.83 kg ha-1). It is remarkable that the genotypes GW 1339, GW 2017-864 and HI 8737 had high performances in both stressed and non-stressed conditions for grain yield. The maximum value of STI (0.576), HARM (4329.06) GMP (4922.03), MP (5612.56) and YI (1.28) indices was manifested by genotype GW 1339. Based on different drought indices, genotypes GW 1339, GW 2017-864 and HI 8737were found promising for drought tolerant than the other genotypes. The STI, HARM, GMP and MP indices, which were strong positive and significantly correlated to the grain yields in both favorable and drought stress environments, were introduced as the best indices, indicating effectiveness of these indices in identifying high yielding lines under drought stress as well as non-stress conditions. Association studies indicated that there was a positive and non-significant correlation between (Yp) and (Ys) was observed. The SSI index exhibited a negative correlation with the yield (Ys) under stress environment. Results of association studies showed that STI, HARM, GMP and MP indices were able to discriminate between drought-sensitive and drought-tolerant durum wheat genotypes. Principal components analysis showed two components which explained 99% variation.