ارزیابی خصوصیات زراعی و عملکرد هیبریدهای جدید آفتابگردان (.Helianthus annuus L) در شرایط تنش کم آبی

In order to study the effects of drought stress on agronomical traits and seed yield of new hybrids of sunflower there individual experiments were conducted on nine hybrids of sunflowers under three irrigation regimes (irrigation after 60,120,180 mm evaporation from evaporation pan class A) in 2006. The experiment was a randomized complete block design with 3 replication, performed in the research field of Karaj Seedling and Seed Breeding Agency. Results showed drought stress had significant effects on some sunflower traits such as number of total and active leaves, final plant height, stalk diameter, head diameter, diameter of empty seed, head weight, stalk weight, 1000 seed weight, seed yield and oil seed percent at the level of 1%. Also the phenological processes of plant, were affected by water deficit stress at the level of 1%. Given hybrids showed significant differences in all traits except head weight. The highest yield was obtained from control trait at 2778 kg.ha-1 decreasing by 62 and 81% under moderate and severe stress, respectively. The highest yield was obtained from A75×R196 and A46×R73 at 1687 and 1630 kg.ha-1, respectively due to head diameter and seed number. Comparison of stress and hybrid interaction levels showed that water deficit had negative effect on all recorded traits. The highest yield was obtained from control trait A112×R82 at 3482 kg.ha-1. A148×R65 and A75×R196 resulted in the highest seed yield of 1394 and 643 kg.ha-1 under moderate and sever drought stress, respectively.