Flesh Color Inheritance and Gene Interactions among Canary Yellow, Pale Yellow, and Red Watermelon

Two loci, C and were previously reported to determine flesh colors between canary yellow and red watermelon (Citrullus lunatus). Recently, lycopene beta-cyclase (LCYB) was found as a color determinant gene for canary yellow (C) and a codominant cleaved amplified polymorphic sequence (CAPS) marker was developed to identify canary yellow and red alleles. The inhibitor of canary yellow (i-C), as reported in a previous work, was not detected in our original family derived from a cross between canary yellow and red parents. To identify additional genetic determinants such as we prepared a new family using 'Yellow Doll' (canary yellow) and 'Sweet Princess' (red), which was reported to carry the inhibitor gene as parents. A new distinct class of flesh color, pale yellow, was identified in the progeny from the new canary yellow x red cross. The predominant carotenoid in canary yellow and pale yellow phenotypes was neoxanthin, followed by violaxanthin and neochrome; pale yellow contained less total carotenoids, but had more minor carotenoids compared with canary yellow. The chi-square goodness-of-fit test indicated that there are two genes involved in determining flesh color among canary yellow, pale yellow, and red, but the segregation pattern did not fit the pattern as reported for an gene. When the genotype of the family 'Yellow Doll' x 'Sweet Princess' was analyzed with our LCYB CAPS marker, the flesh color of every individual perfectly cosegregated with the marker. The new pale yellow phenotype also cosegregated with the marker linked to the C allele, indicating that the recessive py phenotype (pale yellow) must carry at least one of the C alleles for expression. Therefore, we propose to designate py for a pale yellow determinant along with C as a canary yellow determinant. A homozygous recessive py gene resulted in pale yellow flesh color in the presence of a dominant C.