evaluation of drought tolerance in different canola cultivars based on stress evaluation indices in terminal growth duration

in order to evaluate of drought tolerance in different canola varieties based on stress evaluation indices in terminal growth duration, an experiment was conducted as split-plot design on randomized complete block design with four replications at experimental field of seed and plant improvement institute, karaj in 2005 and 2006. results using stress susceptibility index (ssi) and tolerance index (tol) revealed that talaye and opera varieties are more tolerant than other varieties. stress tolerant index (sti) and geometric mean productivity (gmp), that their higher values indicate the tolerance of cultivars under stress, revealed opera, hyola420 and zarfam, as cultivars with highest yield in both optimum irrigation and drought conditions. study of total indices with give attention to that the best cultivars are they have high yield in optimal condition and least decrease in yield at stress condition, introduced opera and zarfam cultivars as suitable cultivars in drought stress condition. study of high and positive correlation between drought tolerance index (sti), geometric mean productivity index (gmp) and mean productivity index (mp) with yield in optimum and drought conditions indicated that them as the best indices for introduce drought tolerant cultivars.