Differential growth, physiological and biochemical responses of niger (Guizotia abyssinica Cass.) cultivars to water-deficit (drought) stress

The present study demonstrates the effect of polyethylene glycol-8000 (PEG) and percent field capacity (FC%)-induced water-deficit stress on growth, water status, productivity and various biochemical parameters in Guizotia abyssinica Cass. cultivars (IGP 76, GA 10, No. 71 and IGPN 2004) at seedling and maturity stages of the plant. Cultivar GA 10 showed higher, IGP 76 and No. 71 moderate, and IGPN 2004 least reduction in percent seed germination given PEG stress treatments (0, 10 and 20%). A similar pattern was observed for decreased growth and water content of the seedlings and plants of the cultivars exposed to both kinds of water-deficit stresses. The productivity (number of capitula per plant, number of seeds per capitula and 1,000-seed weight) and total chlorophyll content of cultivar IGPN 2004 was significantly higher in comparison to other cultivars given different FC% treatments (100, 80 and 60%). Significantly higher accumulation of proline, glycine betaine and total soluble sugars and lower damage to membrane lipids under increased water-deficit stress (i.e., at 80 and 60% FC) conditions in cultivar IGPN 2004 suggested its more tolerance capacity to water-deficit stress in comparison to other cultivars. Besides, antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) partially demonstrated variations in the tolerance of the cultivars to water-deficit stress. The results suggest that cultivar IGPN 2004 could be considered as more tolerant, and IGP 76 and No. 71 as moderately tolerant, whereas GA 10 was more sensitive to water-deficit stress.