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

Effect of water deficit stress on proline contents, soluble sugars, chlorophyll and grain yield of sunflower (Helianthus annuus L.) hybrids

The objective of the present work was to determine the mechanisms of tolerance of four sunflower hybrids; H1 = Azargol, H2 = Alstar, H3 = Hysun 33 and H4 = Hysun 25 to water stress under three different levels of irrigation regimes; WD1 = irrigation after 50 mm (normal irrigation), WD2 = 100 mm (mild stress) and WD3 = 150 mm (intense stress) cumulative evaporation from evaporation pan class A. The results showed that water deficit stress significantly (P≤0.01) increased proline, soluble sugars and chlorophyll b but decreased chlorophyll a, total chlorophyll and grain yield in all sunflower hybrids; therefore increase of the proline, soluble sugar, chlorophyll b and decrease of the chlorophyll a, total chlorophyll and grain yield 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 soluble sugars. Under both mild and intense water deficit stress conditions, the highest value of proline, soluble sugars, chlorophyll a and chlorophyll b were recorded in Alster, Azargol, Hysun 33 and Alstar hybrids, respectively. Also, the highest value of total chlorophyll in both mild and intense water deficit stress conditions was acquired by Hysun33 and Alstar, respectively. The results also indicated that under normal irrigation, mild and intense water deficit stress, maximum grain yield was obtained in Azargol (3448 kg ha-1), Alstar (2121 kg ha-1) and Alstar (829 kg ha-1), respectively. Therefore, among all of sunflower hybrids, Alstar hybrid under both levels of water deficit stress had the best tolerance to water deficiency stress.Key words: Proline, soluble sugars, chlorophyll, grain yield, sunflower

Grain Physical Properties of Some Sunflower Cultivars Influenced by Water Deficit Stress

In order to investigate the water deficit impact on physical characteristics of seed in four sunflower hybrids (Azargol, Allstar, Hysun 33 and Hysun25), under three irrigation regimes (irrigation after 50, 100 and 150 mm cumulative evaporation from class A evaporation pan, respectively) and experiment was conducted. Sampling was done at the end of growing period (season) when the moisture content of the seed was reached to 13%. The results showed that the maximum length, width and seed thickness were obtained from irrigation after 50 mm cumulative evaporation from pan, while irrigations after 100 and 150 mm evaporation caused to decrease the length by 15% and 24%, width by 18% and 35% and seed diameter by 17% and 30%, respectively. Also, the seed width in comparison with length and seed thickness had the most susceptive to water deficit stress levels. The maximum length, width and seed thickness were seen in Allstar variety. Also, Allstar had the highest seed weight for all levels of irrigation. There was no significant difference between Allstar and Hysun 25 in 50mm evaporation. Therefore, the Allstar hybrid had most tolerance to water deficit stress condition under all levels of irrigation in aspect of seed weight and physical properties of seed