Identification of a novel locus C 2 controlling canary yellow flesh color in watermelons.

The flesh color of watermelon is an important trait that is determined by carotenoid composition and affects consumers' fruit desirability. Although a complete dominant control by C locus ( Cllcyb ) for canary yellow flesh (CY) over red flesh has been reported, red and CY colors frequently appear as a mixed pattern in the same flesh (incomplete canary yellow, ICY) in F ₁ and inbred lines carrying dominant C alleles. Therefore, we examined the genetic control of the mixed color pattern in ICY using whole-genome resequencing of three ICY (ICY group) and three CY inbred lines (CY group), as well as genetic linkage mapping of an F ₂ population. The segregation pattern in 135 F ₂ plants indicated that CY is controlled by a single locus (named C ₂ ) dominant over ICY. The whole-genome resequencing of ICY and CY inbred lines revealed an ICY/CY-specific region of approximately 27.60-27.88 Mb on Chr. 2 that was polymorphic between the ICY and CY groups. Our genetic map, using nine cleaved amplified polymorphic sequence markers developed based on the single-nucleotide polymorphisms from the ICY/CY-specific region, confirmed that C ₂ is located on Chr. 2 and cosegregated with the marker (M7) derived from a non-synonymous single-nucleotide polymorphism of the pentatricopeptide repeat (PPR) gene ( ClPPR , Cla97C02G039880 ). Additionally, 27 watermelon inbred lines of ICY, CY, and red flesh were evaluated using previously reported Cllcyb ( C locus)-based markers and our C ₂ locus-linked ClPPR -based marker (M7). As a result, dominant alleles at the C ₂ locus were required to produce CY, in addition to dominant alleles at the C locus, while a recessive homozygous genotype at the C locus gave the red flesh irrespective of the genotype at the C ₂ locus. Using a ClPPR -based cleaved amplified polymorphic sequence developed in this study and Cllcyb -based markers, watermelon cultivars with CY, ICY, and red flesh could be successfully discerned, implying that the combined use of these markers will be efficient for marker-assisted selection of flesh color in watermelon breeding.
Competing Interests: Authors GK and YK were employed by the company Partner Seeds Co., Ltd., and Author BJ was employed by the company UNELL Biotechnology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Park, Shahwar, Jang, Shin, Kwon, Kim, Hong, Jin, Kim, Lee and Park.)