Genetic basis and breeding potential of fruit traits in interspecific F2 populations of watermelon (Citrullus lanatus [Thunb.] Matsum. & Nakai × Citrullus amarus Schrad.)

Watermelon is an economically important fruit crop cultivated worldwide for its nutritional value and commercial importance. However, yield stagnation and limited genetic diversity constrain further productivity gains. To address this constraint, the present study evaluates genetic variability, heritability and the breeding potential of key fruit traits in watermelon using two interspecific F2  populations developed from crosses between a wild Citrullus amarus Schrad. line and two elite Citrullus lanatus [Thunb.] Matsum. & Nakai lines, with the objective of harnessing untapped allelic diversity for crop improvement. Two F2 populations, CL 0732 × CL 0413 (Cross 1 (C1)) and CL 0732 × CL 0695 (Cross 2 (C2)), were evaluated for fruit length, fruit width, rind thickness, total soluble solids (TSS) and fruit weight using standard statistical parameters, including genotypic and phenotypic coefficients of variation, heritability, genetic advance and transgressive segregation index (TSI). Results revealed substantial genetic variability, with high GCV (18.09–85.71 %) and heritability (70.43–97.67 %) across traits, indicating strong additive gene action. While the C2 population exhibited higher trait means, C1 demonstrated superior breeding potential based on standardised range, TSI and usefulness index, suggesting a greater likelihood of recovering superior recombinant inbred lines. Strong positive correlations between fruit weight and fruit length, fruit width and TSS support indirect selection strategies. The findings underscore the value of wild × cultivated crosses for broadening the genetic base of cultivated watermelon. Overall, this research provides a robust framework for identifying promising breeding populations and implementing targeted selection strategies to improve watermelon yield and quality.