Sodicity is a major abiotic stress reducing the yield of a wide variety of crops all over the world. Soil sodicity is a significant crop production constraint around the world. Inherited tolerance is a precursor to pre-breeding and breeding tolerant cultivars. In order to investigate the antioxidant enzymes activity, 17 genotypes of pumpkin for sodicity tolerance studies were taken up at Horticultural College and Research Institute for Women, Tiruchirappalli using Randomized Block Design with three replications. The antioxidant enzyme system of plants plays an important role in the scavenging of Reactive Oxygen Species (ROS) that accumulate during stress and is the first line of defence to counter the deleterious stress effects. Proline content significantly increased in salt-tolerant genotypes under sodic soil condition. Catalase and peroxidase activity which plays a significant role in abiotic stress. Significantly decreased in salt-sensitive genotype while significantly increased in salt tolerant genotypes. The salt-tolerant genotype CM -11 (Madurai) maintained higher levels of chlorophyll (3.7 mg/g) and proline content (428 mg/g) as well as catalase (278 mg of H2O2 g-1 hr-1) and peroxidase activities (272 mg of H2O2 g -1 hr-1) under sodic soil condition followed by CM -12 (Sedapatti) and CM-1 (Old Ayakkudi) which might be the mechanism responsible for sodicity tolerance. These germplasm accessions can be used in further breeding programme.

Highlights

• Soil sodicity is one of the major constraints for the success of afforestation worldwide. High sodicity causes poor soil physical conditions and thus adversely affect plant growth and yield.
• Presence of genetic variation in plant species has tremendous potential to maintain high plant growth and yield under sodic soil. Hence, the present investigation is undertaken with a view to attempt on crop improvement in pumpkin under sodic soil having 8.5 pH and 15 dS/m Exchangeable Sodium Percent.