Selection of Sunflower Cultivars Based on Water Deficit Stress Tolerance, Dry Matter Partitioning and Grain Yield

Dry matter Partitioning in vegetative and reproductive organs and yield of 11 sunflower hybrids were evaluated in different irrigation program during 2013 and 2013 in Karaj, Iran. Three separate experiments including irrigation after 60, 120 and 180 mm evaporation from evaporation pan, Class A as base of randomized complete block design were sutdied as control, mild and severe stress conditions, respectively. The results showed the plant height was decreased by 10.1% under mild stress and 17.2% under severe stress compared to control. Although, increasing of the height had a positive effect on grain yield, but the stem weight was more effective than head weight on grain yield. In control irrigation, plants produced thicker stems that made to translocate more dry matter to the grain. But under severe stress conditions, the  head diameter decreased, and the most of the dry matters were used in the head development. The highest grain to head weight ratio was obtained from mild stress. In severe stress conditions, the grain to head weight ratio  went up and it caused to rise linear growth of grain number and weight. Grain yield was diminished on average of 18% and 33% under mild and severe stress conditions, respectively. In the stress conditions, Barzegar hybrid had the highest grain yield for maintaining the number and weight of grain in the heads. The evaluation of strees susceptibility and tolerant showed that STI, MP and GMP indices had a positive and significant correlation to yield and, Barzegar and Sunbro hybrids were superior thant Cultivars and hybrids.