Abstract
Peel color is an important factor affecting commodity quality in vegetables; however, the genes controlling this trait remain unclear in wax gourd. Here, we used two F2 genetic segregation populations to explore the inheritance patterns and to clone the genes associated with green and white skin in wax gourd. The F2 and BC1 trait segregation ratios were 3:1 and 1:1, respectively, and the trait was controlled by nuclear genes. Bulked segregant analysis of both F2 plants revealed peaks on Chr5 exceeding the confidence interval. Additionally, 6,244 F2 plants were used to compress the candidate interval into a region of 179 Kb; one candidate gene, Bch05G003950 (BhAPRR2), encoding two-component response regulator-like protein Arabidopsis pseudo-response regulator2 (APRR2), which is involved in the regulation of peel color, was present in this interval. Two bases (GA) present in the coding sequence of BhAPRR2 in green-skinned wax gourd were absent from white-skinned wax gourd. The latter contained a frameshift mutation, a premature stop codon, and lacked 335 residues required for the protein functional region. The chlorophyll content and BhAPRR2 expression were significantly higher in green-skinned than in white-skinned wax gourd. Thus, BhAPRR2 may regulate the peel color of wax gourd. This study provides a theoretical foundation for further studies of the mechanism of gene regulation for the fruit peel color of wax gourd.
Highlights
Wax gourd [Benincasa hispida (Thunb.; Cogn.; Cucurbitaceae)] is an annual herb that has been cultivated in China for ~1,500 years and has an annual planting area of >200,000 hm2
118 were green-skinned and 115 were white-skinned in the BC1 population. This distribution conformed to a 1:1 segregation ratio (χ2 = 0.039, p = 0.844)
In the BC1 population, 238 plants were green-skinned, and 234 plants were whiteskinned. This distribution conformed to a 1:1 segregation ratio (χ2 = 0.034, p = 0.854)
Summary
Wax gourd [Benincasa hispida (Thunb.; Cogn.; Cucurbitaceae)] is an annual herb that has been cultivated in China for ~1,500 years and has an annual planting area of >200,000 hm. Peel color is an important commodity quality used to judge fruit maturity and influences consumer preferences. The peel color of Chinese wax gourd may vary: dark or light green, cyan-green, or white. Variability in the chlorophyll, carotenoid, and anthocyanin contents accounts for the color differences among cultivars (Li et al, 2007; Zhu et al, 2016). White-skinned wax gourd is rare, its superior appearance and dense mouthfeel are favored by consumers. Peel color genetics and fine mapping and cloning of the genes regulating
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