Study of some physiological indices, seed yield and its components of rapeseed varieties under drought stress

Evaluating the efficiency of some physiological indices for recognizing water deficit effects, selecting water deficit tolerant fall rapeseed genotypes and also evaluation of drought effects on seed and oil yields and its components were the main goals of this study. The experiment was conducted as factorial based on a randomized complete blocks design with three replications in East Azarbaijan Research Center for Agriculture and Natural Resources during 2010-2011. The experimental factors were irrigation with three levels including: non-stressed (irrigation at 30-35% available soil water depletion), water deficit stress during rosette stage in fall and seed filling stage (irrigation at 70-75% available soil water depletion) and genotype including six genotypes: Karaj 1, Karaj 3, Opera, Okapi, Licord and Modena. The results indicat that water deficit during rosette stage at fall increased leaf temperature and decreased relative water content and stomatal conductance significantly, but effects of drought on seed yield and its components were not significant. Whereas water deficit during seed filling stage, significantly increased leaf temperature and decreased leaf relative water content, stomatal conductance, plant height, yield components except seeds per silique and finally seed and oil yields. Between seed yield with silique per plant significant and positive correlation was seen. It seems that drought stress decreased seed yield mainly by decreasing silique per plant. Indices of leaf temperature, leaf relative water content and stomatal conductance indicated significant correlations with seed yield and therefore can be used for recognizing the effects of drought on rapeseed. The cultivars Okapi and Licord with 4670 and 4518 Kg/ha seed and 1861 and 1758 Kg/ha oil yield, indicated higher performances in cold climate of Tabriz region respectively.