A Comparative Analysis of High-Throughput and Conventional Phenotyping: Validation of Plantarray System and Dynamic Physiological Traits for Drought Tolerance in Watermelon

Drought stress is a major constraint on watermelon production worldwide. Conventional phenotyping methods for drought tolerance are often low-throughput and fail to capture dynamic physiological responses. This study validated the high-throughput phenotyping platform (Plantarray 3.0) against conventional methods by dynamically evaluating drought tolerance across 30 genetically diverse watermelon accessions. The Plantarray system quantified key dynamic traits, including transpiration rate (TR), transpiration maintenance ratio (TMR), and transpiration recovery ratios (TRRs), revealing distinct drought-response strategies. Principal component analysis (PCA) of these dynamic traits explained 96.4% of the total variance (PC1: 75.5%, PC2: 20.9%), clearly differentiating genotypes. A highly significant correlation (R = 0.941, p < 0.001) was found between the comprehensive drought tolerance rankings derived from Plantarray and conventional phenotyping. We identified five genotypes as highly tolerant and four as highly sensitive. The elite drought-tolerant germplasm, notably the wild species PI 537300 (Citrullus colocynthis) and the cultivated variety G42 (Citrullus lanatus), exhibited superior physiological performance and recovery capacity. The results demonstrate that the Plantarray system not only efficiently screens for drought tolerance but also provides deep insights into dynamic resistance mechanisms, offering a powerful tool and valuable genetic resources for breeding climate-resilient watermelon cultivars.