Effects of end-season drought stress on yield and yield components of rapeseed (Brassica napus L.) in warm regions of Kermanshah Province

Abstract

In order to identify drought stress tolerance in 10 rapeseed (Brassica napus L.) varieties (Hyola42, Hyola308, Hyola420, Hyola401, Option 500, RGS003, RGS006, Sarigol, Amica and Kimberly) were evaluated under two conditions (irrigated and drought stress) in Sarpol-e-Zahab region in 2013-2014 growing season. Under drought stress conditions, irrigation was cut from flowering stage. Combined analysis results showed that drought stress had significant effect on plant height, stem diameter, lateral shoot number, biological yield, flowering duration, days to maturity, pod per plant, seed per pod, 1000 seed weight, seed yield and harvest index. Seed yield average reduced from 3955.1 to 2800.96 kg/ha (29.18%) caused by drought stress. Meanwhile pod per plant reduced more than other traits (32.54%). Cultivars were significantly different for all traits except stem diameter, flowering duration, days to maturity. The cultivar × conditions interaction effects were not significant for any traits. Under normal conditions, the Hyola420, Hyola42 and Sarigol cultivars had the highest seed yield respectively. Under drought stress conditions, Sarigol cultivar had the highest seed yield. Regression analysis using backward method showed that stem diameter, biological yield, days to flowering end and oil percent entered to seed yield model and explained 57% of all data variations. Path analysis based on regression analysis results revealed that plant height, pod per plant, seed per pod and 1000 seed weight had the highest direct effect on seed yield. Cluster analysis results indicated that oilseed rape lines were divided to 3 groups under both conditions. Analysis of variance for drought indices showed significant differences between cultivars for MP, STI and GMP. With consideration of correlation between indices and yield under stress and non-stress, these drought indices were identified as the best indices for isolation and selection of drought tolerant cultivars.