Encodes Carotenoid Isomerase and Regulates Orange Flesh Color in Watermelon ( L.).

Flesh color is a significant characteristic of watermelon. Although various flesh-color genes have been identified, the inheritance and molecular basis of the orange flesh trait remain relatively unexplored. In the present study, the genetic analysis of six generations derived from W1-1 (red flesh) and W1-61 (orange flesh) revealed that the orange flesh color trait was regulated by a single recessive gene, (orange flesh). Bulk segregant analysis (BSA) locked the range to ∼4.66 Mb, and initial mapping situated the locus within a 688.35-kb region of watermelon chromosome 10. Another 1,026 F plants narrowed the locus to a 304.62-kb region containing 32 candidate genes. Subsequently, genome sequence variations in this 304.62-kb region were extracted for BSA strategy among 11 resequenced lines (one orange flesh and ten nonorange flesh) and finally narrowed the locus into an 82.51-kb region containing nine candidate genes. Sequence variation analysis of coding regions and gene expression levels supports as the most possible candidate for , which encodes carotenoid isomerase (). This study provides a genetic resource for investigating the orange flesh color of watermelon, with malfunction resulting in low lycopene accumulation and, thus, orange flesh.