Genetic Analysis And Gene Mapping For Green Peel Color In Melon(Cucumis Melo L.)

Peel color is an important quality trait of melon.It is of great significance for melon breeding researching inheritance and gene mapping of peel color.In this experiment,the yellow-peel line B432and green-peel lines,B168 and B421,were used to construct six generations of genetic population?P₁,P₂,F₁,F₂,BC₁P₁,BC₁P₂?to analyze the inheritance of melon peel color.In addition,the BSA-seq and Genome-wide association study?GWAS?were used to locate the genetic loci responsible for melon peel color.The main results were as follows:1.Two genes with additive-dominant-epistatic?E-1 model?with additive-dominant polygene models were fitted to the inheritance of melon peel color.For combination B168×B432,the polygenic heritability of L value and C value in F₂ are 86.78%and 68.41%,and multi-gene heritability are 9.97%and 19.36%;For combination B421×B432,the major gene heritability of the L value and C value in F₂are 96.94%and 69.95%,and the polygenic heritability are 0 and 18.44%.The results showed that the major genes possess higher heritability and the polygenic heritability is lower.So the selection of melon peel color should be performed in the early separation generation during breeding.2.Calculating the separation ratio of melon peel color and carrying out the chi-square test,the results were as follows:Peel color of F₁ are consistently green;The peel color of BC₁P₁ were separated,and the separation ratio consistent with the theoretical value green:white:yellow=2:1:1;The separation ratio green:white:yellow was in accordance with the theoretical value 12:3:1 in F₂ population.It is suggested that the melon peel color was controlled by two genes,of which green has a dominant epistatic effect on white and white is dominant to yellow.3.Selecting 30 green individuals,29 white individuals and 9 yellow individuals from a F₂segregation population?B432×B421?to construct bulking-pools respectively.In addition,the BSA-seq and whole genome resequencing technology were used to locate the genetic loci responsible for melon peel color.The peel color related genes were mapped to the 0.02-5.7 Mb and 0.08-9.5 Mb intervals of chromosome 4 and chromosome 10,respectively.4.By BSA-seq combined with Genome-wide association study?GWAS?,we detected a gene MELO3C003375 that controls melon green peel.By analyzing the sequence alignment between parents,we found that the CDS of MELO3C003375 has a 13 bp deletion in green peel melon.Based on the deletion fragment,we developed an Indel marker and verified it in the F₂ population,which is consistent with the phenotype.The expression level of the MELO3C003375 was analyzed by RT-PCR.The results showed that MELO3C003375 exhibited a significant higher expression in green-peel line than that in white-and yellow-peel lines,suggesting that the gene is a candidate gene for controlling the green peel formation in melon.