determining of effective traits on rapeseed seed yield under semi cold rainfed conditions

to achieve high seed yield of rapeseed varieties under semi cold rainfed conditions; twenty rapeseed varieties were compared in randomized complete block design with three replications in sararood agricultural research station for two years. combined analysis results indicated that there were significant differences at 5% probability level among years for number of days to start of flowering, number of days to end of flowering and number of sub branch and at 1% probability level for pod no. per plant, seed and oil yield. the highest seed yield obtained from 2nd year (1309.15 kg/ha). parade, ebonite and okapi varieties showed the highest seed yield (1697, 1526 and 1478 kg/ha respectively). stepwise regression analysis explained that number of days to maturity and number of sub branch had significant negative and positive effects (-100.129 and 364.035 respectively) on the seed yield. factor analysis extracted two factors. factor loading of first two eigen values showed that first two factors explained 98.443%, of total variance. rates of first and second factors were 55.293% and 43.150%, respectively. the first and the second factor were named productivity factors (seed yield and oil yield with high positive factor loading 0.950 and 0.947) and fixed capital factor (number of day to maturity, plant height and number of sub branch with high positive factor loading 0.729, 0.644 and 0.568), respectively. in general, parade, ebonite and okapi varieties could be recommended for fall planting under rain fed conditions in semi cold area in kermanshah because they had the highest seed yield and earliness. also, we can introduce the less number of days to maturity (earliness) and number of sub branch as selection indices under rain fed conditions in kermanshah.