Efficiency of selection indices in screening bread wheat lines combining drought tolerance and high yield potential

Drought is the most severe production constraint for wheat worldwide. Evaluating performance of bread wheat lines and predicting drought tolerance is an essential part of the breeding process. The objective of this study is to investigate the efficiency of several indices in identifying wheat genotypes combining drought tolerance and high yield potential. Twenty-four indices, which were most frequently used in plant breeding, were compared based on grain yield of 40 bread wheat genotypes grown under two contrasting environments (stressed and non-stressed) during 2 cropping seasons 2014 and 2015. The trials were laid out as completely randomized block design of 3 replicates. Experienced stress was moderate because it caused less than 50% reduction in yield in both seasons. Analysis of variance of grain yield showed significant differences among genotypes, years, sites and genotype × site interaction. All drought indices revealed significant differences among genotypes in both seasons, except GM, SNPI and ATI. Based on correlations and principal component analysis, repeatable strong positive correlations were found between the indices (MP, MRP, REI, GMP, STI, MSTIk1, MSTIk2, HM and RDY) and grain yield under both moisture conditions during the two seasons. These indices can be considered as suitable criteria for selection of drought tolerant and high yielding genotypes under moderate stress Mediterranean environment. Moreover, these indices were able to select the highest mean yields under 20% of selection pressure with low variation across environments; especially STI, GMP and MP. The genotypes “Gladius” (9) and “AUS30355” (11) were consistently selected in both environments during two cropping seasons.   Key words: Triticum aestivum, drought stress, tolerance indices, grain yield.