Effect of water stress on yield and yield components of sunflower hybrids
A field experiment during year 2009 was conducted in the research station of the University of Tehran, College of Abouraihan in Pakdasht region, Iran. The study was aimed to investigate the effect of water stress on seed yield, yield component and some quantitative traits of four sunflower hybrids namely Azargol, Alstar, Hysun 33 and Hysun 25 under three different irrigation regimes; irrigation after 50 (normal irrigation), 100 (mild stress) and 150 (intense stress) mm cumulative evaporation from evaporation Pan class A. The experiment was laid out as a split plot design based on randomized complete block design (RCBD). The results showed that, water stress significantly (P > 0.05) decreased seed yield, yield components and seed oil content but increased the seed protein content in all the sunflower hybrids. The highest seed yield of 2591 kg ha-1 was obtained from normal irrigation. An increase of the seed protein content and a decrease of the seed oil content occurred when water input decreased. Although at different level of water stress, each hybrid behaved differently according to their genetic makeup. Alstar hybrid exhibited the highest value for all the mentioned characteristics, except for seed oil and protein contents. The results also indicated that, under normal irrigation, mild and intense water deficit stress, maximum seed yield was obtained by Azargol (3448 kg ha-1), alstar (2121 kg ha-1) and alstar (829 kg ha-1), respectively. Therefore, alstar hybrid under both levels of water deficit stress conditions in respect of seed yield and related traits such as seed number per head, 1000 seed weight and head diameter had the highest tolerance to these conditions. However, with normal irrigation, Azargol hybrid produced the highest seed yield.
Key words: Seed oil content, seed yield, sunflower, water deficit stress, yield component.