Relationship between duration and rate of seed filling of rapeseed (Brassica napus L.) genotypes at three layers of upper, middle and bottom of plant affected by fall and winter sowing dates

Growth characteristics, phenological stages, and yield components of crops are affected by environmental conditions and can affect seed yield. The present study evaluated the duration and rate of seed filling at three layers of upper, middle, and bottom, seeds number per plant, and seed yield of five rapeseed genotypes (RGS003, Dalgan, Zabol10, Hyola401, and Hyola4815) in 6 planting dates of fall (7-Oct, 17-Oct, and 27 Oct) and winter (9-Feb, 19-Feb, and 1-Mar). Two separate experiments were performed in autumn and winter as split plots in a randomized complete block design with three replications at the research field of Seed and Plant Improvement Institute, Karaj, Iran in 2015-2016 growing seasons. In each experiment, planting dates and rapeseed genotypes were considered as the main plots and sub-plots, respectively. The results of this study showed that the values of seed yield, single seed weight, seed filling duration, and seeds per plant decreased with delay in planting, especially in winter planting dates. The number of seeds per plant was more effective in final yield formation than the single seed weight, seed filling rate, and seed filling duration. The Dalgan genotype, although having a moderate single seed weight, seed filling rate, and seed filling duration, had the highest seed yield due to its greater number of seeds per plant. Also, the rapeseed genotypes produced the highest grain yield in Oct 7 and Feb 9 planting dates in the fall and winter seasons, respectively.