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An experiment was conducted in the seed and plant Improvement Institute at karaj researches station to evaluate the response of sunflower under normal and water stress conditions in 1993 and 1994. Eight hybrids were evaluated for thirty four physiological , morphological , and phenological traits. Factor analysis was used to analyse the data.Under normal condition eight main and independent factors accounted for 91% total variations. The grain yield and days to maturity contributed 57.3% of total variations . Other factors were biomass at flowering time , duration of reproductive period photosynthesizing unit and translocation of photosynthesized materials, 1000 - seed weight, and length of root, respectively .Under water stress condition, seven factors contributed 89.6% of total variations in data . Reproductive period 9 root length ,height plant and stalk diameter showed 60.5% of total variations alone. Other factors were grain yield 1000-seed weight, dry matter weight of head at flowering , leaf number and oil percent of seed
respectively.Results shows that selection for longer reproductive period
higher stalk diameter , taller plant height , and greater grain yield are considered to be best selection index for developing drought tolerant varieties
• Under normal condition , selection for grain yield, duration of growing period, and oil seed percent are more suitable.