Biplot analysis for assessing morphological variation and drought tolerance in seven species of Brassica

In this experiment 36 accessions of seven species of Brassica genus were evaluated under field condition (for study of genetic variation) and under laboratory condition (for study seedling drought tolerance) in 2012 at Isfahan university of technology research farm. The statistic design in field was completely randomized block with three replications. Results of field assessments were suggestive of considerable variation between accessions for all of the measured traits with better performance for B. carinata with respect to seed yield. The results of principal component analysis showed that three independent factors explained 71 percent of total variability. In second experiment، accessions were evaluated under three levels of water deficit treatment (zero، -3 and -6 bar caused by PEG) in germination stage according to a factorial experiment based on the completely randomized design with three replications. Results indicated that for most of the traits، effect of water deficit levels، genotypes and their interaction were significant. Rootlet length was the most sensitive trait and increased by decreasing drought stress. Results of drought tolerance indices (such as TOL and STI) also confirmed that wild species such as B. nigra، B. oleracea and B. juncea may tolerate drought at least in germination stage. According to principal component analysis، B. fruticulosa and B. napus were found as the most sensitive and B. nigra، B. oleracea and B. juncea as the most drought tolerant species; hence the latter species can be used as a good sources of genes for improving cultivated species in breeding programs