Investigation of Natural Variation in Gas Exchange, Water Relations, and Quantum Yield among Sweet Gourd Hybrids

Sweet gourd (Cucurbita moschata Duch ex Poir) has a high production volume in Bangladesh and holds third rank next to eggplant and radish. Salinity affects almost all growth and physiological aspects of the plant development and eventually reduces yield. Identifying salt tolerance among genetic resources and breeding populations is a valuable study for solving salinity problems. This research aimed to find sweet gourd hybrids tolerant to salinity. Sixteen sweet gourd hybrids (F1) were used for testing salt stress tolerance levels. Salinity stress was induced in pot soil by adding NaCl solutions (4, 8, 12, 16, and control 0.35 dS m-1). The experiment was conducted from October 2019 to March 2020 in a randomized complete block design with three replications. The research was conducted at the Horticulture Research Centre, Bangladesh Agricultural Research Institute (BARI), Gazipur. The measurements included changes in gas exchange parameters against photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (E), quantum yield (Fv/Fm), and relative water content (RWC). Results showed that the gas exchange traits and RWC in all hybrids decreased under stress compared to the control. Photosynthetic parameters in sweet gourd hybrids responded susceptibly to salt stress, thus suppressing overall growth under salinity stress. The reduction of gaseous exchange traits and RWC were minimal in P11 × P12 and P6 × P14. The highest Fv/Fm and RWC occurred in P11 × P12 at 8 dS m-1 salinity stress. The highest Fv/Fm and RWC appeared in P6 × P14 and P11 × P12 hybrids at 12 and 16 dS m-1 salinity stress, so the hybrid P11 × P12 appeared salt tolerant.