Differential Response of Two Contrasting Melon (Cucumis melo L.) Genotypes to Drought Stress

The present study aims to gain insights into the response mechanisms of drought stress tolerance among two contrasting melon (Cucumis melo L.) genotypes. Drought stress was imposed by polyethylene glycol (10%) for 7 days and various physiochemical and molecular characteristics were analyzed on different days of drought stress treatment. Results revealed that the drought-sensitive genotype (MG-II) was significantly affected by drought stress, as evidenced from the elevation in hydrogen peroxide (H2O2), malondialdehyde content (MDA), and electrolyte leakage (EC). Furthermore, drought stress significantly hindered the vegetative growth, chlorophyll fluorescence, photosynthetic pigments, and leaf gas exchange characteristics of MG-II genotypes. In contrast, the drought-resistant genotype (MG-I) exhibited a robust response to drought stress, characterized by marked upregulation in the antioxidant enzyme genes and activities, which in turn resulted in a decrease in oxidative damage and improved vegetative growth and photosynthetic functions. Additionally, transmission electron microscopy (TEM) revealed that the oxidative damage triggered by drought stress was more severe in the MG-II genotype, which exhibited an irregular chloroplast shape compared to the MG-I. These findings may potentially enhance our comprehension of coping strategies involved in drought stress tolerance and provide materials for future melon breeding and molecular studies.