Study of Genetic Variation and Drought Tolerance in Commercial Rapeseed (Brassica Napus L.) Cultivars

In order to identify drought stress tolerance in rapeseed, nine commercial rapeseed cultivars (opera, karaj1, karaj2, karaj3, zarfam, okapi, talayeh, licord and modena) were evaluated under two conditions (normal and drought stress) in kangavar region in the west iran in 2014-2015 growing season. this research was carried out in a split plot experiment based on completely randomized design in four replications. under drought stress conditions, irrigation was cut from end of flowering stage. analysis of variance results showed that drought stress had significant effects on plant height, days to maturity, pods per main branch, pods per subbranch, pods per plant, seeds per pod, 1000 seed weight, oil yield and seed yield. seed yield reduced from 4036.9 to 2919.4 kg/ha (27.68%) and oil yield reduced from 1840.8 to 1362.2 kg/ha (25.99%) caused by drought stress. oil yield reduced from 1840.8 to 1362.2 kg/ha (25.99%) caused by drought stress. meanwhile pods per subbranch reduced more than other traits (27.93%). there were significant differences among cultivars for all studied traits. the karaj3 and talaye cultivars showed the highest seed yield in normal (4632.5 kg/ha) and stress (3747.5 kg/ha) conditions respectively. the interaction effects of cultivar and irrigation conditions was significant just for plant height (p<0.05) and oil yield (p<0.01). the karaj3 cultivar showed the highest mp (4172.5), gmp (4147.06), sti (1.055) drought indices. with consideration of correlation between indices and yield under stress and non-stress, these indices (except the ssi and tol) were identified as the best drought indices for isolation and selection of tolerant cultivars.