Investigation and selection index for drought stress in durum wheat (Triticum durum Desf.) under Mediterranean condition

Drought is a wide-spread problem seriously influencing durum wheat (Triticum durum Desf.) production and quality, but development of resistant cultivars is hampered by the lack of effective selection criteria. The objective of this study was to evaluate the ability of several selection indices to identify drought tolerant cultivars under varying environmental conditions. Ten durum wheat cultivars were evaluated under both moisture stress and non-stress field environments using a randomized complete block design for each of the environment. Six drought tolerance indices including stress susceptibility index (SSI), stress tolerance index (STI), yield stability index (YSI), mean productivity (MP), harmonic mean (HMP) and geometric mean productivity (GMP) were used. The indices were adjusted based on grain yield under drought and normal conditions. Yields in the normal condition were not correlated with yields in the stress condition, better stress susceptibility index (SSI) was associated with low yield under normal conditions, and therefore this index could not identify cultivars with good performance in both stress and non-stress condition. The significant and positive correlation of GYp and MP, GMP and STI showed that these indices were more effective in identifying high yielding cultivars under different moisture conditions. Stress tolerance index (STI) gave identical cultivar classification with the geometric mean (GMP), both being better than SSI in identifying top yielders in contrasting water availability conditions. The results of calculated gain from indirect selection from moisture stress environment would improve yield in moisture stress environment than selection from non moisture stress environment. Wheat breeders should, therefore, take into account the stress severity of the environment in choosing an index