Deficit irrigation impact on lycopene, soluble solids, firmness and yield of diploid and triploid watermelon in three distinct environments

Water conservation practices are critical for production and quality of watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] in southern regions of the USA. The objective of this experiment was to determine the effects of deficit irrigation and environment on lycopene content, total soluble solids, firmness, and yield of diploid and triploid watermelon. Irrigation rates were 1.0 evapotranspiration (ET), 0.75 ET, and 0.5 ET, which were calculated based on climatic parameters applied to the Penman-Monteith equation. Diploid cultivars were ‘Summer Flavor 710’ and ‘Summer Flavor 800’, and triploid cultivars were ‘Summer Sweet 5244’ and ‘Super Seedless 7187’. To investigate if there was a consistent response in cultivars across diverse environments, three studies were conducted in remote Texas locations: Uvalde in the Wintergarden, Weslaco in the Rio Grande Valley, and Lubbock in the High Plains. To isolate the environmental effects due to weather and soil type, all experiments used similar cultural strategies (plant spacing, subsurface drip irrigation, black plastic mulch, and containerized transplants), except for transplanting and harvesting dates. Deficit irrigation reduced total marketable yield by 36% at Uvalde, 30% at Lubbock, and 15% in Weslaco, increasing the yield of small fruits (<5 kg). Location and irrigation rates had major influences on yield of diploid and triploid watermelon. Soluble solids content increased with deficit irrigation at 0.5 ET rate in triploids, but not in diploids. Flesh firmness also increased in triploids compared to diploids. Fruit lycopene content increased with maturity (7 and 22 d after ripening) at all irrigation rates and cultivars. This work across three diverse Texas locations confirms that deficit irrigation directly reduced yield, but does not reduce lycopene development and fruit quality of triploid watermelon.