Genotypic Variation in Drought Response of Wax Begonia (Begonia semperflorens-cultorum) Under Controlled Irrigation Regimes

Drought stress is a major constraint to the sustainable production of ornamental bedding plants, particularly under increasing water restrictions and climatic variability. This study evaluated the morphological and physiological responses of five wax begonia genotypes (FB08-059, 183-11, OPGC 5104, ‘Cocktail Vodka’, and ‘Sprint White’) under three irrigation regimens: routinely watered (three times per week), weekly watered, and nonwatered. Over an 8-week greenhouse trial, genotypes were assessed for growth index, shoot and root biomass, chlorophyll content, chlorophyll fluorescence (Fv/Fm), and anthocyanin accumulation. Results revealed significant genotypic differences in drought tolerance. FB08-059 and 183-11 consistently outperformed commercial cultivars in growth, biomass retention, and maintenance of photosystem II efficiency under both moderate and severe drought conditions. These genotypes also exhibited higher chlorophyll content and delayed pigment degradation compared with ‘Sprint White’ and ‘Cocktail Vodka’, which showed rapid physiological decline and poor survival in the nonwatered treatment. Contrary to expectations, anthocyanin content decreased under drought stress in all bronze-leaved genotypes, with FB08-059 maintaining the highest levels under routine and moderate irrigation. This study identifies FB08-059 and 183-11 as promising candidates for breeding drought-resilient wax begonias, combining ornamental quality with abiotic stress adaptation.