Construction Of High-density Genetic Map And QTL Mapping Of Peel Color In Wax Gourd

Wax gourd?Benincasa hispida Cogn.?,also known as cold gourd?anpillow gourd,is an annual climbing plant of the genus Benincasa Savi of cucurbitaceae.It has rich nutritional value and medicinal value.And it is the special vegetable that our country supplies in the South and North.Wax gourd peel color is one of the important commodity qualities.Bright peel color can increase the value of the commodity and meet people's requirements for the replacement of vegetable varieties.Basic research such as genetic map construction,QTL mapping and candidate gene prediction can provide a deep understanding of the biological functions of wax gourd,and provide important theoretical guidance and technical methods for directed molecular breeding.In this study,the dark-green peel male parent?kx-2?and the yellow-white peel female parent?yo-16?were used as materials to construct the F₂generation mapping group,and the whole genome of wax gourd population was re-sequenced.We developed SNP markers based on sequencing results and constructed high-density genetic map of wax gourd.After that,combined the peel color and the genetic map to complete QTL mapping.Finally,use the reference genome annotation information to annotate the genes in the mapping interval,and predict the candidate genes that control the peel color of wax gourd.The main results of this research are as follows:1.According to the peel color and chlorophyll content of the male parent,female parent and F₁generation,it was found that the dark green peel of the gourd was not completely dominant to yellow-white,and F₁generation had the middle peel color of the two parents,light green.The peel color of F₂generation was counted and analyzed,and it was found that the peel color trait of F₂group showed continuous variation.It can be inferred that the peel color traits of wax gourd belong to quantitative inheritance.2.Whole genome re-sequencing technology sequencing was performed toward 241 F₂gourd and parents,a large number of SNP markers have been developed and a high-density genetic map of wax gourd has been constructed,including 12 linkage groups and 5072 SNP markers,with a total of genetic distance of 3130.35 c M,and an average distance of 0.62 c M.At present,the genetic map of wax gourd has the largest number of molecular markers and is constructed for the first time using whole genome re-sequencing technology.3.Through the combination of high-density genetic map and F₂group phenotype data,QTL mapping of the peel color of wax gourd was performed.A total of two QTLs were detected,namely Bpc.8.1 and Bpc.8.2,located in the genetic interval of 84 c M-156.6 c M on eighth linkage group.The phenotypic variances were 8.1%and 6.53%,the LOD were 3.02063 and 2.859935,respectively,and guessed Bpc.8.1 may be the QTL that control the dark green peel of wax gourd.4.Based on the QTL mapping results,20 genes were found in the candidate interval,of which 11 genes were successfully annotated.Among them,Bch8G004450 annotation results were related to chloroplast outer membrane pore protein,Bch8G004050 annotation results wererelated to chloroplast constituent proteins encoded by nuclear genes.Therefore,it was inferred that Bch8G004450 and Bch8G004050 may be candidate genes for controlling the dark green peel of wax gourd.