evaluation physiological characteristics and grain yield canola cultivars under end seasonal drought stress in weather condition of ahvaz

to evaluate canola cultivars response to physiological characteristics and grain yield end seasonal drought stress in weather condition of ahvaz, farm experiments were done at research farm of khuzestan agriculture and natural resources center. during 2007-2008 and 2008-2009 crop years. farm test comprised drought stress was done as split plot form with randomize complete block design with four replication, treatments consist of drought stress (main factor) including 50, 60 and 70 percent of water use content, which was applied from early heading stage until physiological maturity, and three spring canola cultivar including shirali, hayola 401 and r.g.s. were considered as sub plots. measurements include biological yield, grain yield, harvesting index, number of pod per plant 1000 grain weight, number of grain in pod, plant height, and stem diameter, oil and protein percentage. results showed that drought stress reduced significantly grain yield, biological yield, harvest index and the average of reduction of them during 2 years for per unit reduce moisture from 50% to 70% were 2, 1.35, and 0.81 percent, respectively. during two years, 1000 grain weight, number of pods per plant and number of grain per pod reduced 27, 36 and 20 percent, respectively. terminal drought stress reduced significantly plant height, stem diameter, stem number per plant and pod length, this reduced were 12, 46, 36 and 14 percent, respectively. stem diameter, and stem number per plant reduced more than other characteristics. in this study oil grain decreased 12 % and protein grain increased 18.5% but oil and protein yield decreased 44.9% and 27.1% respectively..finally, in weather condition of khuzestan, terminal drought stress on february and march in which has simultaneous with early flowering stage and filling seed, significantly, reduced yield and compounded yield and affects on stem growth and qualities oil and protein negatively. therefore, with irrigation management and selection resistance genotypes to drought stress, canola production could be increased.