Identification of Tolerate Rapeseed (Brassica napus L.) Cultivars to Drought Tolerance Indices under Late Sowing Date

Water resource limitation in the end of growth season of rapeseed crop is one of the main problems for production and development of this crop in semi-arid regions of Iran. Therefore, introduction of compatible and tolerate cultivar to this condition is crucial for growth expansion of rapeseed. To identify and introduce suitable rapeseed cultivar for delayed planting, a split plot experiment based on randomized complete block design with three replications at Research Field of Seed and Plant Improvement Research Institute of Karaj, Iran was conducted in 2015-16 and 2016-17. In this study, sowing dates were October 7 (normal) and November 6 (delayed planting) asseinged to the main plots, and rapeseed cultivars including ES Hydromel, ES Alonso, ES Darko, ES Lauren and Ahmadi to the sub-plots. To introduce of tolerate cultivar to drought tolerance indices, experimental plots were subjected to two common irrigation conditions (control) and irrigation interruption from the flowering stage onwards (drought stress). Combined analysis of data indicated that delayed planting significantly reduced rapeseed oil percentage and oil yield. According to the results ES Hydromel cultivar produced the highest oil percentage (41.61%) and oil yield (1381.08 kg.ha-1). Based on the selected indices of this study, including geometric mean productivity, stress tolerance index, and mean productivity, the most tolerant cultivar under both normal and delayed planting was ES Hydromel and the least tolerant cultivar under normal conditions was ES Lauren and under stress conditions was ES Darko. The results of cluster analysis also confirmed the formation of two clusters, ES Darko, Ahmadi and ES Lauren in belonged to sensitive cluster and ES Hydromel and ES Alonso to the tolerant cluster.