Physiological and Yield Performance Is Partially Linked to Water Use Efficiency of Eggplant Genotypes in a High-Tech Glasshouse

Eggplant (Solanum melongena L.) has become an increasingly common vegetable grown in glasshouses. This study emphasized on the physiological traits and productivity of three eggplant cultivars (Longa, Lydia, and Tracey) in a high-tech glasshouse to determine the genotypic differences of agronomical, morphological, and physiological responses. The physiological parameters as well as the productivity of these eggplant cultivars were evaluated. The results showed that Tracey had significantly higher leaf growth than Longa and Lydia. Longa exhibited significantly higher values of net CO2 assimilation (A), stomatal conductance (gs), and transpiration rate (Tr) than Tracey, whereas Tracey showed significantly larger gs, Tr, and intracellular CO2 concentration (Ci) than Lydia. Tracey showed a significantly higher number of flowers per node compared to the two other varieties, but the number of fruits did not statistically differ among cultivars. Tracy produced the highest yield (fruit weight and fruit yield per m2) due to the significantly higher leaf length and leaf expansion rate despite the lowest level of A among the three cultivars. Interestingly, the higher yield of Tracey translated into better water use efficiency (WUE) in the agronomic term, but its intrinsic WUE (A/gs) was the lowest among the three cultivars. However, significant correlations between photosynthetic parameters and WUE were only found in certain stages of eggplant growth. Therefore, further research work with an emphasis on the source and sink partitioning of a large number of eggplant genotypes is required to investigate the varietal performance of greenhouse eggplants. Then, the information can be translated into protected cropping to set up the growth benchmark for large-scale sustainable production of eggplants with better yield and less water consumption for the horticultural industry.