Comparison of yield based drought tolerance indices in improved varieties, genetic stocks and landraces of potato (Solanum tuberosum L.)

Drought strongly influences potato (Solanum tuberosum) production and quality. Potato being a drought susceptible crop, the development of varieties with enhanced tolerance to water stress could highly improve productivity in drought prone areas. The objective of this study was to evaluate the ability of several yield based indices to be used in large scale screening for drought tolerance. The experiment included improved varieties, genetic stocks and landraces potatoes grown under drought and irrigated conditions. A group of accessions with high yield under both conditions was identified. Mean productivity (MP), geometric mean productivity (GMP), tolerance (TOL), drought tolerance index (DTI), drought susceptible index (DSI) and yield stability index (YSI) were calculated from tuber yield under drought and irrigated conditions. The relationships between these indices and yield were analyzed. The Fleiss' Kappa concordance test was used to analyze the correspondence between accessions previously identified as highly productive under both drought and irrigated conditions and accessions with optimal values for the different indices. MP, GMP and DTI allowed identifying genotypes combining high yield potential and high yield under drought within the three subsets of genotypes. Conversely, DSI, YSI and TOL showed low and variable concordance values across subsets, suggesting that their efficiency in screening genotypes highly depends on the nature of the tested genetic material.