Screening Drought Tolerant Rapeseed Cultivars Using Yield and Physiological Indices

Rapeseed (Brassica napus) is an important source of edible oil worldwide. Rapeseed production is adversely affected by water deficit stress in drought prone areas. This study aimed to evaluate drought tolerance in seventeen rapeseed cultivars using yield and physiological indicators. The field experiment using two irrigation regimes was conducted on a silty loam soil at the research station of School of Agriculture, Shiraz University, Shiraz, Iran. In each irrigation treatment, the seventeen rapeseed cultivars with different origins were grown in a randomized complete block design with three replications. The normal irrigation and drought stress treatments were irrigated when 40% and 70% of available soil water capacity were depleted, respectively. The results revealed highly significant differences among the rapeseed cultivars for seed yield, and the various yield and physiological indices. The yield under normal and drought stress conditions showed significant correlations with stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean productivity (HMP) and modified stress tolerance index (MSTI) implying these indicators are able to identify the high yielding drought tolerant rapeseed cultivars. Based on the reliable yield indices, the three-dimensional plot and biplot analysis showed that the cultivars Karaj 1, NK Octans and Modena were the high yielding drought tolerant rapeseed cultivars. Generally, the drought tolerant cultivars showed high relative water content (RWC) under stress conditions, however there was no strong association between drought tolerance and RWC.