Mapping and predicting a candidate gene for flesh color in watermelon

摘要

The color of watermelon flesh is an important trait determined by a series of carotenoids.Herein,we used Cream of Saskatchewan(pale yellow flesh)and PI 186490(white flesh)as parental materials for an F2 segregation and initial mapping using the bulked segregant analysis sequencing(BSA-seq)strategy.The BSA results revealed a flesh colorrelated QTL that spans approximately 2.45 Mb on chromosome 6.This region was preliminarily positioned in a 382-kb segment,and then narrowed down into a 66.8-kb segment with 1260 F2 individuals.A total of nine candidate genes were in the fine mapping interval,but only Cla007528(encoding chlorophyllase)had non-synonymous mutations and was significantly expressed between the parental materials throughout flesh development.We also checked the expression patterns of the carotenoid metabolic pathway genes based on RNA-seq data and qRT-PCR validation.Three genes in the xanthophyll cycle(ClCHYB,ClNCED-1 and ClNCED-7)exhibited differential expression patterns between the two parental lines at different flesh color formation stages.ClPSY1,ClPDS,ClZDS,ClCHXE,ClCRTISO and ClLCYB also exhibited clearly different expression patterns accompanied by carotenoid accumulation.