Development Of SSR Molecular Marker And Genetic Diversity-analysis Of Pepper(Capsicum Frutescens L.)

Pepper(C frutescens L.),as one of clutispecies pepper in the world,include both of wild and cultivated species in China.Wild Capsicum frutescens is the important resource of Capsicum frutescens and is the only wild pepper specie in China.In addition there are many desirable traits in C.fritescens,such as,hign temperatuer resistance and moisture resistance?disease resistance?barren resistance?low light tolerance?high fruit setting rate per plants fresh and tender fruit,etc.Based on these advantages,the Pepper(C frutescens L.)can be used as material basis for improving the existing cultivated pepper.In this study,SSR molecular markers were developed on basis of wild pepper genome sequencing,and SSR molecular markers were futher used to analyze the genetic diversity of global shrub pepper germplasm resources.These studies are of great significance to understand the genetic richness and relationship between germplasm,expand the germplasm basis of pepper,and finde and utilize excellent genes,so as to provide material basis for improving the traits of cultivated pepper and improve the efficiency of genetic breeding.In this study,SSR loci identification in pepper genome,SSR molecuar markers development,diversity analysis of 96 pepper materials were completed,results as follows:(1)A total of 301211 SSRs were detected from pepper genome using software MIS A.Among them,the number of three-base repeats was the largest,170727,accounting for 56.7%;followed by two-base repeats,102982,accounting for 34.2%;The number of the six-base repeats is minimum,4114,accounting for 1.4%.Among 301211 SSRs,AT was the deminant motify type(41566,13.8%);followed by TTG(31356,10.42%).Based on the distribution of SSRs on chromosomes,it was found that the most of SSRs were located on Chr12 and the most dense of SSRs were distribured on Chrll,with 116.55/Mb,and the average distance between the two SSRs was 8.58 Kb.These results will provide valuable information for the development of SSR molecular markers.(2)A total of 22 paies SSR polymorphic primers were selected from 240 pairs SSR piers using 8 pepper materials from different countries as the template.The size of 22 paris of primers were 21-26bp,Tm:57.1-71.3 ?,the size of amplification fragment was about 200bp,which conform to the principle of SSR primer design.Hence these primers can be used for genetic diversity analysis of pepper.(3)The molecular genetic diversity of 96 pepper varieties was analyzed by 22 polymorphic SSR primers.The cluster analysis showed that 96 pepper varieties could be divided into 7 major groups according to 0.72 Jaccard' s similarity,and could be divided into 17 maj or groups according to 0.74 Jaccard' s similarity.The genetic diversity analysis showed that the mean value of allele number(Na),effective allele number(Ne),expected heterozygosity(He),observed heterozygosity(Ho),Shannon-Weaver index(?)and polymorphism information content(PIC)were 5.2273,2.8460,0.6039,0.5069,1.1572,0.5555 respectively.Suggestig that the 96 pepper varieties had rich genetic diversity,which could be as material basis for improving the existing cultivated pepper.