RÉSUMÉ
Stem color is an important agronomic trait of wax gourds. However, its regulatory genes have not been identified. In this study, 105 inbred lines constructed from two parents (GX-71 and MY-1) were sequenced and quantitative trait loci sequencing was used to mine the genes that regulate stem color in wax gourds. The results identified two quantitative trait loci related to stem color, qSC5 and qSC12, located on Chr05 (11,134,567-16,459,268) and Chr12 (74,618,168-75,712,335), respectively. The qSC5 had a phenotypic variation rate of 36.9% and a maximum limit of detection of 16.9. And the qSC12 had a phenotypic variation rate of 20.9%, and a maximum limit of detection of 11.2. Bch05G003950 (named BchAPRR2) and Bch12G020400 were identified as candidate genes involved in stem color regulation in wax gourds. The chlorophyll content and expression of BchAPRR2 and Bch12G020400 were significantly higher in green-stemmed wax gourds than in white-stemmed ones. Therefore, BchAPRR2 and Bch12G020400 were considered the main and secondary regulatory genes for wax gourd stem color, respectively. Finally, InDel markers closely linked to BchAPRR2 were developed to validate the prediction of wax gourd stem color traits in 55 germplasm lines, with an accuracy of 81.8%. These findings lay the foundation for exploring the genetic regulation of wax gourd stem color and future research on wax gourd breeding.
RÉSUMÉ
Anthocyanins are a group of flavonoids found in buckwheat (Fagopyrum esculentum) and many other plant species; however; little is known about their mechanisms of synthesis and regulation in buckwheat. We previously reported a spontaneous mutant buckwheat line that shows the green stem phenotype; this line does not accumulate anthocyanins but synthesizes flavonol and proanthocyanidin in the stem. Here, we used this line and lines developed by this line to search for genes related to anthocyanin accumulation in buckwheat. The lines with green stem showed flavonoid-3-O-glucosyltransferase activity against UDP-glucose, indicating that the flavonoid-3-O-glucosyltransferase gene was not controlling the green stem trait. We therefore searched the buckwheat genome database for a gene encoding glutathione S-transferase (GST), a flavonoid-binding protein that transports flavonoids to the vacuole, and identified a candidate gene, FeGST1. Expression analysis showed that FeGST1 was expressed in wild type buckwheat but not in the green stem lines. Linkage analysis with an F2 segregating population produced by crossing between the green stem line and a self-compatible line showed that FeGST1 segregated with stem color without any recombination. This indicates that the green stem trait could be caused by homozygous non-functional alleles of the FeGST1 locus.
