Effect of irrigation water deficit on antioxidant activity and yield of some sunflower hybrids

Sunflower (Helianthus annuus L.) is one of the most important oil-producing plants that it can tolerate short periods of water deficit (WD). The objective of this study was to evaluate the effects of water stress on the physiological and agronomic characteristics of four sunflower hybrids. A two-year field experiment was carried out using a randomized complete block design with four replications and a split plot arrangement. The irrigation treatments were applied based on 60 mm (full-irrigated), 120 mm (moderate water deficit) and 180 mm (extreme water deficit) of evaporation from the 'class A' pan evaporation. The results showed that water deficit, compare to full-irrigated, significantly increased the activity of all antioxidant enzymes in leaves such as Superoxide dismutase (SOD), Glutathione peroxidase (GPX), Glutathione reductase (GR) and Catalaz (CAT). The correlation results showed that the seeds number per head was main yield components associated to seed yield when sunflower plants were grown under the full-irrigated and extreme water deficit. The results showed that the Euroflor and Allestar hybrids had highest seed yield in full and limited irrigation condition, respectively. The correlation results showed that there was a high, positive and significant correlation among seed yield and CAT in water irrigation deficit condition. Moreover, the GPX and CAT content can be used as a drought tolerance index to selection tolerant genotypes under moderate and extreme water deficit conditions.