Exogenous application of melatonin mitigate the heat stress in different tomato (Solanum lycopersicum L.) cultivars

Heat stress alleviates yield and production of horticultural crops and is considered a major risk for sustainable agriculture. Melatonin acts as a first line soldier to regulate plant growth by creating a conducive environment under heat stress. Thus, the present study was performed in pots to mitigate the adverse impact of heat stress on four genotypes of tomato (two were heat sensitive and two were heat tolerant) through exogenous application of melatonin. The experiment was comprised of two treatments, control and foliar spray of melatonin @ 25 mu M, under factorial design (CRD) with five replications by using heat-sensitive and heat-tolerant cultivars of tomato as a test crop. All the tomato varieties were treated with 25 mu M melatonin through foliar spray and compared with control which remained untreated. All the growth and yield parameters and enzymatic activities of antioxidants including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were increased significantly due to the application of melatonin. Moreover, the melatonin spray enhanced the osmolyte production such as malondialdehyde (MDA), proline contents, total soluble sugars, and fruit quality over control treatment. Concludingly, the heat-tolerant cultivars performed better under melatonin spray as compared to heat-sensitive cultivars of tomato.