Waterlogging influences the physiology index and antioxidant enzyme activity in Cucurbita maxima and Cucurbita moschata

Waterlogging is one of the major environmental challenges that can adversely impact squash growth, development, and productivity. Nevertheless, studies on the physiological changes of squash to waterlogging stress are scarce. Previously, we reported that the Cucurbita moschata (Cmo) Early Price (Ep) cultivar showed higher chlorophyll content (CC) and spectral reflectance compared to the Cucurbita maxima (Cma) OK-101 (Ok) cultivar after waterlogging. In the present work, we further examined more physiological parameters in eight cultivars of Cmo and Cma, and studied whether these non-destructive indices could efficiently identify various waterlogging-tolerant genotypes and were consistent with visual evaluations. Moreover, we investigated the effects of waterlogging on the antioxidant system of cucurbit species, and evaluated dynamic changes occurring in these plants during varying waterlog periods by determining physiological characteristics. The activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD) showed a significant increase in Ep plant leaves and roots after 72 h and 6 h of waterlogging, respectively, compared to Ok plants. In addition, Ep exhibited a higher tolerance to waterlogging than Ok in terms of enhanced root length, values in CC, spectral reflectance, and APX and SOD activity, plus decreased levels of electrolyte leakage, 2,2-diphenyl-1-picrylhydrazyl free radical scavenging, and hydrogen peroxide levels. This study provides a comprehensive understanding of the physiological variations in response to waterlogging stress and can potentially be used to breed cucurbit species with waterlogging tolerance for a wetter future climate.