Response of antioxidant enzyme activities and root yield in sugar beet to drought stress

In order to evaluate the response of antioxidant defense system of three sugar beet genotypes to drought stress and enhancing management of soil water content, a two-years field experiment was conducted at the Research Site of Sugar Beet Seed Institute in Karaj, Iran during 2008 and 2009. Irrigation treatments arranged in main plots during growing seasons included: 80 mm (I1: as control), 130 mm (I2) and 180 mm (I3) evaporation from A class pan under surface irrigation method, 30 mm (I4), 80 mm (I5), 130 mm (I6) and 180 mm (I7: as severe drought) evaporation with 100% volume of water requirement under trickle irrigation (Tape) method and 30 mm (I8) evaporation with 75% volume of water requirement under trickle irrigation (Tape) method. Genotypes included: 7112 (G1), BP-Karaj (G2) and BP-Mashhad (G3) were in sub plots. Results of the study showed that drought stress decreased root yield (RY) increased the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) in sugar beet leaves. There were significant differences among genotypes for antioxidant enzyme activity. Also, irrigation × genotype interactions showed significant difference on CAT and GPX activities. There was a negative correlation between enzymes activities and RY. Results of the study also indicated that water deficit stress causes production of reactive oxygen species (ROSs), which results in greater membrane permeability i.e., malondialdehyde (MDA) content and oxidative stress in the plants. Moreover, genotypes having greater levels of antioxidants showed better resistance to drought stress.