Evaluation of Drought Tolerance of Rapeseed (Brassica napus L.) Genotypes in Laboratory and Field Conditions

To evaluate response of rapeseed genotypes to drought stress, an experiment was performed in germination and later growth stages in laboratory and field conditions at Razi University, Kermanshah, Iran during 2005-2006 cropping season. Germination test under controlled conditions was done using a completely randomized design with factorial arrangement of four drought levels in three replications and field study was conducted based on a randomized complete block design in stress and non-stress conditions in three replications. In laboratory, the results indicated that with decline of water potential (from zero to -12 bar), most of germination traits were significantly reduced and shootlet length was the most affected trait from water stress. According to GSI there was a significantly different between genotypes and levels of drought stress, thus the highest GSI, was related to genotype Licord. In general, based on all germination characteristics Dante and Licord were tolerant genotypes in early stage of growth. In field, the result of ANOVA showed that there were significant differences among genotypes for all drought tolerance indices and yield in both conditions. Analysis of correlation between yields (in stress and non-stress conditions) and drought tolerance indices showed that STI, GMP and MP were suitable indices for screening rapeseed genotypes to drought stress and genotype Zarfam had the highest yield and highest counts for STI, GMP and MP. Thus it was selected as a tolerant genotype with high yield.