SCREENING OF NORTH AFRICAN BARLEY GENOTYPES FOR DROUGHT TOLERANCE BASED ON YIELDS USING TOLERANCE INDICES UNDER WATER DEFICIT CONDITIONS

Water deficit is one of the most constraining factors for the growth, development and yields of plants in arid and semi-arid regions of the world. The objective of this study is to evaluate North African barley collection for drought tolerance and to study the tolerance indicators of water deficit in order to select the most relevant ones that could be used for assessing any large scale plant population. For this purpose, two trials were conducted: first one was conducted in the laboratory to evaluate the germination characteristics of sixteen North African barley genotypes under physiological stress conditions induced by polyethylene glycol-6000 and the second one was conducted in the field on the same genotypes, under favorable and water deficit conditions. In the first experiment, germination parameters showed significant differences between genotypes within the same water regime and between different water regimes and revealed the tolerance of the majority of the Egyptian genotypes to drought. In the second experiment, yields, relative water content (RWC) and drought tolerance indicators also showed the same trend where the majority of Egyptian genotypes as well as one Tunisian genotype tolerated drought more than others do. STI (Stress Tolerance Index), SSI (Stress Sensitivity Index), YSI (Yield Stability Index) and TOL (Stress Tolerance) indices showed different correlations to conclude that (STI) and (YSI) are the best predictors of drought tolerance compared to other indices. On the other hand, a positive correlation between root length under physiological stress and field yield under water deficit conditions has been established, allowing selection of the most drought-tolerant genotypes at an early stage (germination) before evaluating them in the field.