Morpho-physiological response of rapeseed (Brassica napus L.) genotypes to drought stress

This study was conducted to evaluate the physiological indices in relation to screening of rapeseed genotypes for drought tolerance, and to study seed yield and seed yield components under early and late season drought stress. Six rapeseed genotypes were evaluated under non-stressed and water deficit conditions during rosette and seed filling stages. The experiments were conducted in East Azarbaijan Agricultural and Natural Resources Research and Education Center, Iran for 2 years (2010-2011 and 2012-2013). According to the results, canopy temperature (Tc) was increased, stomatal conductance (Kl) and relative water content (RWC) were decreased significantly by drought stress during the rosette and seed filling stages. Correlations among the aforementioned physiological traits at seed filling stage with each other and with seed yield were significant. It seems that these physiological traits can reflect the drought effects in rapeseed genotypes. Among the genotypes, significant differences were observed for Kl at seed filling and RWC at rosette stages. While, Okapi and Licord having the highest seed yield, presented the highest Kl during seed filling and RWC at rosette stages. Therefore, Tc, Kl and RWC can be used to screen rapeseed genotypes for tolerance to drought stress. Drought stress during the seed filling stage significantly decreased plant height, the number of siliques per plant, 1,000-seeds weight and seed yield. Results of path analysis indicated that plant height and yield components indicated positive direct effect on seed yield. Plant height had the highest direct effects on seed yield. Among the genotypes, Okapi and Licord were more suitable for cultivation in normal and drought conditions.