Abstract
The flesh color of watermelon (Citrullus lanatus) is an important fruit quality trait that helps to determine fruit attractiveness and is potentially beneficial to human health. Previous inheritance analyses determined that a single dominant gene, Yscr, produces the scarlet red flesh color rather than the coral red flesh color in watermelon. However, no genomic region or gene-based molecular markers for the locus Yscr have been reported thus far. In the present study, two high-density genetic maps and whole-genome variation detection aided by genome resequencing were first map the flesh color locus Yscr to a small region on chromosome 6 based on two independent populations derived from two scarlet red-fleshed lines and two coral red-fleshed lines. Two major quantitative trait loci located in the same genomic regions were identified in the F2 and BC1P2 populations and explained 90.36% and 75.1% of the phenotypic variation in flesh color, respectively. Based on the genetic variation in the two parental lines, newly developed PCR-based markers narrowed the Yscr region to 40 Kb. Of the five putative genes in this region, four encoded glycine-rich cell wall structural proteins, which implied that a new regulatory mechanism might occur between scarlet red- and coral red-fleshed in watermelon. Moreover, the genotypes of two newly developed InDel markers (InDel27_fc6 and InDel28_fc6) were completely consistent with the phenotypes in the F2 and BC1P2 populations and all 56 scarlet red-fleshed watermelon accessions. The results presented here provide valuable information for marker-assisted selection of flesh color breeding and the functional validation of candidate genes in watermelon.
Highlights
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is enjoyed worldwide for its fleshy, sweet, and juicy fruit and is often consumed in hot weather
Two high-density genetic maps and whole-genome variation detection aided by genome resequencing were used to first map the flesh color locus Yscr to a small region on chromosome 6 based on two independent populations derived from two scarlet red-fleshed lines and two coral red-fleshed lines
These results suggested that scarlet red flesh in watermelon is controlled by a single dominant gene, which is in agreement with the previous genetic analysis of the dominance of the Yscr locus (Gusmini and Wehner, 2006)
Summary
Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] is enjoyed worldwide for its fleshy, sweet, and juicy fruit and is often consumed in hot weather. Wehner summarized the flesh color genes (Wehner, 2012) B (yellow flesh) (Shimotsuma, 1963), C (canary yellow flesh) (Poole, 1944), i-C (inhibitor of canary yellow) (Henderson et al, 1998), Wf (white flesh) (Shimotsuma, 1963; Robinson et al, 1976), Yscr (scarlet red flesh) (Gusmini and Wehner, 2006), Ycrl (coral red flesh) (Porter, 1937; Poole, 1944; Henderson, 1989; Henderson et al, 1998), y° (orange flesh), and y (salmon yellow flesh) (Henderson, 1989; Henderson et al, 1998)
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