Evaluation of terminal drought stress tolerance in spring and winter rapeseed genotypes

To evaluate terminal drought stress tolerance in rapeseed cultivars, field experiments was carried out using split plot arrangements in randomized complete block design with four replications in Karaj Research Field Station, Seed and Plant Improvement Institute, Karaj, Iran in two successive growing seasons (2004-2005 and 2005-2006). Irrigation in two levels; optimum irrigation and no-irrigation from silique formation till end of life-cycle were assigned to main plots. Rapeseed genotypes including; Licord, Okapi, SLM 046, RGS 003, Hyola420, Option500, Zarfam, Orient, Opera, Talaye, Sarigol and Hyola401 were randomized in sub-plots. Results showed that drought stress decreased plant height, number of branch.plant-1, number of silique.plant-1, number of grain.silique-1, 1000 grain weight, grain yield, and oil yield, but increased harvest index. However, it had not significant effect on grain oil content. There were significant differences among cultivars for all measured traits. SLM046 and Zarfam in optimum irrigation had the highest grain yield (3771 kg.ha-1 and 3727 kg.ha-1, respectively) as well as in drought stress conditions (2705 and 2663 kg.ha-1, respectively). These cultivars had the highest oil yield. Therefore, Zarfam and SLM046 can be considred as stable cultivars in optimum irrigation as well as in terminal drought stress conditions.