Assessment of stress tolerance in barley (Hordeum vulgare L.) advanced breeding lines under semi arid conditions of the eastern high plateaus of Algeria

The yield of 186 F-4 barley breeding lines, under stress and non-stress conditions, utilizing four stress indices: S (stress susceptibility index); P (yield deviation between genotype and best genotype in given environment); b (regression coefficient) and PCA (principal component analysis) scores, was investigated in an experiment carried out at the Agricultural Research Station of the Field Crop Institute of S,tif (Algeria). The results indicated significant differences between lines, with a grain yield mean ranging from 127.3 to 1246.6 g m(-2) over the four cropping seasons and a genotype x environment variance component 1.83 higher than the genotypic variance component. S index identified divergent plant material under stressed and unstressed environments. Yield differential between lines with high and low S index was large, limiting the use of the S index to compromise between high yield and adaptability. Lines with low S values are high yielding under stress but are less responsive when growing conditions improve. Low P index identified lines with high yield in the unstressed environment and poor yield under stress conditions, while high P identified lines performing poorly in both environments, suggesting that P index was able to integrate both yield potential and yield stability. Lines with a slope b < 1 showed similar grain yield as those with high P or low S values. Lines with of slope b = 1 have average yield, and as such combine average yield, adaptability and stress resistance. Because of their close mutual relationships, the indices were represented by the first principal component of the PCA, suggesting that PC (principal component) scores would be more appropriate to integrate yield potential and adaptation to variable environments.