Construction Of Genetic Map And QTL Analysis Of Capsaicinoids For Pepper

Pepper is one of the most economically important vegetable crops. Capsaicinoids have been widely used in food and for pharmaceutical purposes and the content of capsaicinoids are inherited quantitatively. An F2 genetic mapping population was derived from the cross between 12H-56(C. frutescens) and 12H-55(C.frutescens) which were specific genetic resources of Yun Nan province. F2 population was used for joint analysis of capsaicin and dihydrocapsaicin content using mixed major gene plus polygene inheritance model. Construction of the genetic map and QTL analysis were carried out based on SSR marks and intraspecific F2 population. The present research focused on sequence of genes which played a role in the capsaicin biosynthetic pathway and then analyzed gene expression of different stages. The results of this research are as follows:1. The method of major gene plus polygene mixed inheritance model was used to analyze the traits of capsaicin and dihydrocapsaicin content. The results demonstrated that the two traits were fit for B-1 model, and the inheritability ratio of major gene reached to 65.80% and 75.49%, respectively.2. To check if there was any sequence difference, full-length c DNA sequences of genes including 4CL, ACL, ACS, BCAT, C3 H, C4 H, FATA, HCT, PAL, PAMT and Pun1 which obtained from two accessions were compared. The results of sequences alignment revealed that there was no difference between the two accessions of genes 4CL, ACL, ACS, BCAT, C3 H, C4 H, FATA, PAMT, Pun1 except HCT and PAL. Finally, basing the different sequence of HCT, new markers, DC1, DC3, DC6, were developed. Analysis expression of genes that played a role in capsaicin biosynthetic pathway revealed that 4CL, BCAT, C4 H, PAMT, Pun1, HCT, COMT had different expressional trend. Combined With capsaicinoids in different stages of fruit development, HCT may led to the difference of content of capsaicinoids.3. A total of 143 markers were screened from 1227 markers including SSR and Indel to construct genetic map. Using Joinmap software, we constructed two linkage maps through regression and maximum likelihood method. However the map using regression method was faster, and the distance of markers was accurate. Then we added new markers to the G2 map. The new map G3 included 16 linkage groups, 146 markers, and the map covered a genetic distance of 934.92 c M, and the average distance between markers was 7.48 c M.4. The software QTL ICimapping 4.0 was used to conduct QTL analysis of quantitive traits basing G3 map and phenotype of F2 population. Totally 11 QTLs were detected on LG1, LG11, LG12 and LG16 group, which could explain the phenotypic variation from 5.01% to 28.88%. Among the QTLs, there were two QTLs, q Cap-12-1 and q Dicap-12-1, distributed between GPMS187 and AM396 together.