Determination of drought tolerant genotypes in Brassica napus L. based on drought tolerance indices

Drought stress is one of the most important dangers for increasing the yield and good production of crops in Iran and the world. To evaluate the genetic diversity of rapeseed genotypes, identifying the drought resistance indices and drought tolerant genotypes, 16 genotypes were tested in a randomized complete block design (RCBD) with three replications and two different water regimes (Irrigated and rainfed) in experimental field of college of Agriculture, Razi university in 2007-2008. In this research, most of drought tolerance indices such as stress susceptibility index (SSI), tolerance index (TOL), stress tolerance index (STI), yield index (YI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HAM) and yield stability index (YSI) based on grain yield were calculated in two different irrigiation regimes. Analysis of variance for grain yield indicated that there were highly significant differences between the genotypes for Yp, Ys, and index GMP, STI, YI and MP. Bi-plot diagram based on two principal componentcomponents indicated that genotypes number 8, 7, 4 and 1 are next to vectors of MP, GMP, STI and HAM and distribution of genotypes in biplot represented the genetic diversity among genotypes for selecting them based on drought tolerance. According to results of drought tolerance indices, Dante, SLM-O46 and Sahara cultivars have higher grain yield and STI index than other genotypes in two regimes and identified as suitable cultivars for production in drought stress condition.