Evaluation of growth and seed yield of new winter oilseed rape (Brassica napus L.) genotypes under terminal drought stress conditions

Breeding and production of drought tolerant cultivars for arid and semi-arid area is very important. The present experiment was carried out to evaluate the effects of drought stress on seed yield and yield components of oilseed rape as well as identification of high yielding and drought stress tolerant genotypes. Eighteen new winter oilseed rape lines and commercial cultivars were evaluated under three moisture conditions in two cropping seasons (2014-2016) in agricultural research station of Islamabad-e-Gharb, Kermanshah, Iran. The three moisture conditions included: full irrigation, irrigation withhold from the flowering and from silique development stages. Results showed that among the yield components, numbers of seeds per silique and 1000-seed weight were significantly affected by drought stress. The reduction in 1000-seed weight under irrigation cut off from silique development stage and flowering stage was 12.8% and 24.4%, respectively. Cumulative reduction in yield components under drought stress conditions caused a significant decrease in grain yield by 32.3% and 41.3%, under irrigation cut off from silique development and flowering stage, respectively. Correlation analysis showed that there was a weak relationship between yield in full irrigation and drought stress conditions, therefore, using drought tolerance indices to screen genotypes with high yield potential and drought stress tolerant is essential. Three dimensional diagrams based on seed yield in full irrigation condition, irrigation cut off condition from silique development stage and STI showed that genotypes GKH2624, GKH3705, Nima, Neptune, GKH0224 and HW118 were located in group A, while under irrigation cut off condition from flowering stage genotypes GKH2624, GKH3705, Nima, Neptune, GKH0224, HW118, Wpn6 and L155 were classified in group A. In general, according to biplot derived from principal components analysis and 3-D graphs, under severe drought stress (irrigation cut off from flowering stage), genotypes WPn6, HW118, Nima and GKH2624 were identified as drought tolerant genotypes with high yield potential.