Production and quality of mini watermelon under salt stress and K+/Ca2+ ratios

ABSTRACT Nutritional management can be an efficient strategy to mitigate the effects of salinity on fruit production and quality. This study aimed to evaluate the production and quality of fruits of mini watermelon crop, Sugar Baby cultivar, grown in a protected environment, under salt stress and K+/Ca2+ ratios. The study was carried out in a greenhouse, using a randomized block design, 1 + 5 scheme, resulting in six treatments and four replications. Six nutrient solutions were employed, one using low-salinity water, with NaCl (0.5 dS m-1) and standard nutrient solution (S1, control treatment), and the others using salinized water at 5.0 dS m-1 (S2) and extra addition of K (S3 = 50% and S4 = 100%) and Ca (S5 = 50% and S6 = 100%). The production (fruit production, longitudinal and transverse diameter of fruit, rind thickness, pulp firmness) and postharvest quality (soluble solids, vitamin C, titratable acidity, and maturation index), in addition to the variables related to the color of the pulp (lightness, chroma index, and Hue angle) were evaluated. The addition of NaCl reduced fruit production, longitudinal, and transverse diameter of fruit, rind thickness, and vitamin C content. Among saline nutrient solutions, extra addition of 50% K (S3) attenuates the deleterious effects of salt stress on the production variables and vitamin C content. Under salt stress, extra addition of 50% K (S3) and 100% Ca (S6) intensifies the red color of the pulp.

摘要 养分管理是缓解盐胁迫 (salt stress)对果实产量与品质影响的有效策略。本研究旨在评估保护地栽培条件下，盐胁迫与不同K+/Ca²+比例对"Sugar Baby"品种迷你西瓜果实产量及品质的影响。试验于温室中开展，采用随机区组设计，设置1+5方案，共包含6个处理、4次重复。试验共设置6种营养液：其中1组采用低盐度水（添加NaCl至电导率0.5 dS·m⁻¹）配合标准营养液（记为S1，为对照处理）；其余5组均采用电导率5.0 dS·m⁻¹的盐化水，分别额外添加钾（K）（S3组添加50%、S4组添加100%）与钙（Ca）（S5组添加50%、S6组添加100%）。本试验测定的指标包括产量相关指标（果实产量、果实纵径与横径、果皮厚度、果肉硬度）、采后品质指标（可溶性固形物 (soluble solids)、维生素C (Vitamin C)、可滴定酸度 (titratable acidity)及成熟指数），以及果肉颜色相关指标（亮度、彩度指数及色调角 (Hue angle)）。NaCl添加会降低果实产量、果实纵径与横径、果皮厚度及维生素C含量。在盐胁迫营养液处理组中，额外添加50%K的S3组可缓解盐胁迫对产量相关指标及维生素C含量的有害影响。盐胁迫条件下，额外添加50%K的S3组与100%Ca的S6组可加深果肉红色程度。