RELATIONSHIP BETWEEN ANTIOXIDANT ENZYME ACTIVITES AND AGRO-PHYSIOLOGICAL TRAITS IN SUNFLOWER LINES UNDER FIELD WATER DEFICIT STRESS

The present study was carried out to determine as to whether changes in the activities of antioxidant enzymes and some other attributes could be used as drought tolerance markers in eight sunflower lines (RGK15, RGK21, RGK25, RGK26, AGK2, AGK30, AGK46, AGK330, produced at Khoy Agricultural Research Station) at the Research Station of University of Tabriz. Under control and field water deficit stress during two growing seasons (20142015) were carried out. Under water deficit stress, the plant height, RWC as well as chlorophyll content (SPAD) were decreased significantly compared to the control condition in all sunflower lines. In contrast, water deficit stress enhanced significantly three superoxide dismutases (SOD), two peroxidases (PDX) and catalase (CAT) isozymes activities as well as proline and malondialdehyde (MDA) contents in nearly all lines. The total phenolics and H2O2 remained genotype dependent and showing highly significant stress x line interactions. The total protein content was not influenced significantly by water deficit stress and genotype differences. So, it seems that the increment of antioxidant enzyme activities and key organic osmolyte contents could be useful tools for drought tolerance genotype screening. Of different antioxidant enzymes and osmolytes analyzed, two PDX activities, proline and MDA contents were found to be a reliable marker of water deficit stress tolerance in the set of sunflower lines examined. These markers were substantially higher in relatively drought tolerant AGK46 sunflower line.