Construction Linkage Maps And Identification Of Quantitative Trait Loci Associated With Major Agronomic Traits In Purple-fleshed Sweetpotato

The construction of molecular genetic map and QTL mapping are the basis of gene cloning,comparative genomics and molecular marker-assisted selection breeding.Therefore,the genetic map construction of sweetpotato has great significance for sweetpotato breeding.At present,the genetic map construction of sweetpotato was mainly based on white-fleshed and yellow-fleshed sweetpotato,but there were few studies on purple-fleshed sweetpotato.QTL mapping was mainly focused on quality traits,such as starch content,dry matter content andβ-carotene content,followed on resistant traits and yield traits,which was consistent with sweetpotato breeding goals and trends in China.Desired agronomic traits are also the important objects in sweetpotato breeding,but breeding technologies are still absent.In this study,the genetic linkage maps of Xuzishu 8 and Meiguohong were constructed by SSR molecular markers,and 5 upground agronomic traits and 2 quality traits were mapped.The main results are as follows:1.We analyzed 8854 EST-SSR sequences from the sequencing results of Xuzishu 8 transcriptome.These SSR were mainly concentrated in si-,di-and tri-nucleotide repeat types,accounting for 88.86%of the total SSR.The SSR length ranged from 10 bp to 240 bp,with an average of 30.3 bp,and the motif number was 127.A total of 110 pairs polymorphic SSR primers with clear and stable bands were screened from 439 pairs of SSR primers from three sources by Xuzishu 8 and Meiguohong and their 2randomly F₁ individuals,and 70 of which were designed in the present study.The polymorphism of 110pairs primers were evaluated through the parents and F₁ individuals.The results showed that each pair of primer could amplify 1 to 10 bands,with an average of 4 bands per pair,and the average primer polymorphism information content value was 0.5653,which indicated that the SSR primers developed in this study had good polymorphism and high application value.2.The 110 polymorphic SSR primer pairs were used to amplify 274 individuals derived from a cross between Xuzishu 8（female）and Meiguohong（male）,and 220,219 SSR markers were generated from Xuzishu8 and Meiguohong,respectively.The female parent map contained 24 linkage groups,including 144 SSR markers,and covered 1325.8 c M with an average marker interval of 9.2 c M.The male parent map contained 21 linkage groups,including 132 SSR markers,and covered 1088.6 c M with an average marker interval of 8.2 c M.3.Using Map QTL 5.0 software to map the QTLs for 7 agronomic traits of sweetpotato,including branch number,vine diameter,longest vine length,petiole length,internode length,dry matter content and anthocyanin content,and identified total 16 QTLs.One QTL related to branch number explains53.2%of the phenotypic variance,1 QTL related to internode diameter explains 16.7%of the phenotypic variance,2 QTLs related to longest vine length explain 9.5%and 13.7%of the phenotypic variance,2 QTLs related to petiole length explain 8.8%and 11.3%of the phenotypic variance,5 QTLs related to internode length explain the phenotypic variance from 9.6%to 28.1%,1 QTL related to dry matter content explains 5.8%of the phenotypic variance,and 4 QTLs related to anthocyanin content explain the phenotypic variance from 8.3%to 54.9%,respectively.