Effect of selenium foliar application on some quantitative and qualitative characteristics of rapeseed cultivars under end-season thermal stress

     Selenium has a protective and positive effect on the quantitative and qualitative characteristics of the plants. In order to investigate the effect of selenium foliar application on leaf proline content and some quantitative and qualitative characteristics of rapeseed cultivars under end-season thermal stress, a factorial split plot experiment was conducted in a randomized complete block design with three replications for two years (2014-2016) in Karaj, Iran. In this experiment, the first factor was planting date on October 15 (timed planting), October 25 (relatively late planting) and November 5 (delayed planting), the second factor was selenium in two levels, including non-application and application of 30 grams per liter of sodium selenate and third factor was genotype, including a commercial cultivar, two promising lines and three foreign commercial hybrids, so that the first and second factor were factorially in the main plots and the third factor was split plot as in sub plot. The results showed that quantitative and qualitative characteristics of rapeseed in this experiment were affected by planting date. Delay in planting reduced winter survival, biological yield, seed yield, crown diameter, relative water content of leaves of rapeseed genotypes. Furthermore, the delay in planting caused a significant increase in the crown water and leaf proline content in the rosette stage, but did not have a significant effect on the harvest index of the genotypes. Selenium foliar application improved the winter survival, biological yield, seed yield, crown diameter and relative water content of leaves of rapeseed genotypes. Selenium foliar application also significantly reduced leaf proline content in the rosette stage, which was an important factor in tolerance of genotypes to delayed planting and end-season thermal stress. In terms of winter survival, seed and biological yield, the L72 line showed the best response to these traits in timed planting, but in terms of delayed planting, Opera was better than the other genotypes, although there was no significant difference with the L72 line.