Deficit Irrigation Effects on Gas Exchange, Root Growth and Fruit Yield of Melons, Poster Board #332

Cultivar evaluations for drought tolerance and irrigation management are very important in water-limited, arid regions of the United States. This study was conducted to investigate the effect of deficit irrigation (50% vs. 100% crop evapotranspiration, ETc) on three melon (Cucumis melo L.) cultivars (Mission and Da Vinci, reticulatus type and Super Nectar, inodorus type). Overall, deficit irrigation significantly reduced photosynthetic rate (Pn) by 30% and stomatal conductance (gs) by 21%. The highest average Pn (20.53 µmol·m^-2·s^-1 of CO₂) and gs (0.31 mol·m^-2·s^-1 of H₂O) were recorded in Mission and Super Nectar, respectively. Transpiration rate and leaf water use efficiency were not significantly affected by either irrigation or cultivar. Throughout the development period, physiological traits were affected by cultivar and irrigation regimes. At fruit set Pn and gs were reduced with deficit irrigation in all cultivars but recovered only in cv. Da Vinci. Deficit irrigation significantly enhanced root length density (RLD; cm·cm^-3) in cv. Mission (120%), decreased RLD in ‘Da Vinci’ (19%) and did not affect in ‘Super Nectar’. Deficit irrigation significantly reduced marketable yield (43%) in cv. Super Nectar but not in cvs. Mission and Da Vinci. Thus, cv. Super Nectar (inodorous type) appeared to be more sensitive to drought stress, likely through reduction in Pn. Da Vinci and Mission (reticulatus type) exhibited some drought tolerance, showing no yield reductions along with improved Pn and RLD, and thus are better choices in water-limited regions.