Physiological and Agronomic Response of Rapeseed (Brassica napus L.) Genotypes To Late-Season Drought Stress under Karaj Climatic Condition

In order to investigate the effect of late-season drought stress on some physiological traits, yield and yield attributes, a two-year field trial was carried out at the research field of Seed and Plant Improvement Institute, Karaj, Iran, on 2015-2017 growing seasons. Factorial arrangement of the treatments was set up as randomized complete block design with three replications. Experimental factors consisted of irrigation regimes (normal irrigation and withholding irrigation from silique setting stage until the end of the growing season) and 17 new winter genotypes of rapeseed. Several physiological traits included relative water content (RWC), total chlorophyll, proline as well as grain yield and yield attributes as dependent variables were measured. Results showed that amount of total chlorophyll under withholding irrigation was reduced (21.65 percentage) reduced compared to the normal irrigation, while leaf proline content was increased by 28.04 %. According to the findings of this study, superior genotypes were not necessarily top in terms of proline. Averaged over both years, Artist genotype produced highest grain yield (5043.25 kg.ha-1) under normal irrigation condition, while L72 and HL3721 had highest grain yield (3915.25 and 3892.45 kg.ha-1, respectively) under withholding condition. It is worth noting that this advantage was mainly revealed to increased source capacity (number of silique plant-1, silique length and number of seed silique-1) as well as the superiority of chlorophyll content and relative water content of the leaf.