Prediction of adaptability and yield stability of durum wheat genotypes from yield response in normal and artificially drought-stressed conditions

Adaptability, yield stability and yield reliability of durum wheat breeding lines are usually assessed through regional testing. The opportunity of partially substituting such testing by evaluation under normal and artificially drought-stressed rainfed conditions was investigated for a water-limited Italian region. Nine lines were grown at six sites for three seasons to assess adaptability across locations as Perkins and Jinks' slope of genotype regressions (beta), stability across environments as Shukla's stability variance (sigma(2)), mean yield (Y), and Eskridge's reliability (R) from Y plus sigma(2). Heterogeneity of genotype regressions explained 54% of genotype-location interaction variation. The beta values were strictly associated (r = -0.99) with genotype scores on the first genotype-location interaction principal component (PC1), were not related to earliness of heading, and tended to negative correlation with plant stature that was hardly explainable in terms of resistance to lodging. Mean yield, PC1 score and rainfall of sites were correlated. The lines were also grown under normal and stress conditions at four sites for two seasons. The stress was established by placing metal channels between the rows that evacuated a portion of rainfall from the end of tillering stage onwards. Predictions of beta, sigma(2), Y and R, attempted respectively from slope of genotype-stress level interaction (beta(p)), beta(p)(2), mean yield across conditions (Y-p), and Y-p plus beta(p)(2), were assessed as genetic correlation. Predictions based on beta(p) and Y-p computed over all test environments were all relatively good, whilst those based on data of individual seasons or locations were mostly inaccurate for sigma(2), Y and R. High-yielding sites could better predict Y and R, Two seasons' data from one such site showed correlations of 0.60, 0.53, 0.72 and 0.75 for prediction respectively of beta, sigma(2), Y and R. Evaluation of advanced breeding lines under normal and artificially stressed conditions at a high-yielding site may prove useful for reducing the number of lines promoted to subsequent regional testing and/or restricting their regional testing to specific areas of adaptation.