Screening of Rapeseed (Brassiac napus L.) Genotypes for Tolerance to Terminal Heat Stress by Plastic Greenhouse

The majority of rapeseed in Iran is produced in South hot-dry and North hot-humid regions making it necessary to improve heat resistant cultivars. In order to identify heat tolerant and susceptible cultivars, nine spring varieties of rapeseed including commercial cultivars and promising lines, were evaluated under normal and heat stress conditions in research field of the University of Tehran in two sets of randomized complete blocks with three replications for two years during 2015-2016. Heat stress applied by a plastic greenhouse at flowering stage equipped with electric heater. The temperature exceeding 25.1- 39.40C inside the plastic sheet, remarkably different temperature with the open field, significant yield loss of the varieties under stressed condition in both years, illustrated that plastic greenhouse could be effectively used for applying heat stress. Based on grain yield in normal and heat-stressed conditions and tolerance indices, Roodi22, Dalgan and Mahtab were semi-tolerant while Safi5 and DH13 were shown to be the most tolerant and susceptible varieties which might be considered in production and also breeding programs.