| Capsicum is a significant vegetable crop in China.It originated from the tropical region of America and belongs to Solanaceae.It is an annual or perennial herb and is widely planted in the world.There are many cultivated and wild species of pepper,including 5 cultivated species(C.annuum,C.baccatum,C.chinense,C.frutescens,and C.pubecens)and more than 20 wild species.Among them,C.annuum is the most widely planted plant in China and has the most abundant varieties.There are great genetic differences between C.annuum and the other 4 cultivars in fruit size,shape,odor and color.However,under the pressure of high intensity artificial selection,the genetic basis of C.annuum becomes narrower and the genetic diversity index decreases gradually,which hinders the cultivation of new varieties of pepper.It is important to collect and analyze the genetic diversity of pepper germplasm resources to change the relatively narrow genetic background of pepper germplasm resources in China.In addition,distant hybridization is one of the main ways to introduce effective exogenous genes,and interspecific hybridization is an effective way to broaden the genetic background of cultivated pepper and to development germplasm resources.Based on this,in order to broaden the genetic basis of cultivated pepper and enhance its genetic potential,genetic diversity analysis was carried out on 147 germplasm resources of shrub pepper collected in this study,and interspecific hybrids were created using cultivated pepper species C.annuum ’PI194879’ as female parent and wild pepper species C.chacoense ’PI639651’ as male parent.The main research results are as following:1.Genetic diversity of the pepper resource.With the newly developed next generation sequencing technology,genome sequences of C.frutescens can be generated,which are now available for identifying SSR markers via data mining.In this study,278,425 SSRs were detected from the pepper genome using MISA software totally.It was observed that trinucleotides were the dominant repeat motif.This was followed by dinucleotides;tetranucleotides;pentanucleotides;and the hexanucleotides repeat types.In addition,a total of 240 SSR primers evenly distributed over all 12 chromosomes were designed and screened against eight C.frutescens cultivars.Thirty-three SSR markers of them,which have high polymorphism,have been scrutinized for 147 accessions from 26 countries.The dendrogram constructed clustered these accessions into seven major groups.The groups were found to be consistent with their origins.The results obtained in this study provided resources of SSR molecular markers and insight into genetic diversity of the C.frutescens.2.In this study,interspecific hybrid F1(C.annuum×C.chacoense)was produced with cultivated species(C.annuum ’PI194879’-female)and wild species(C.chacoense’PI639651’-male).To identify the authenticity of interspecific hybrids,analysis of morphological observation,pollen viability and SSR molecular markers were employed on hybrid F1 and their parents.Our results showed that(a)great difference was found in agronomic traits between hybrid F1 and their parents,and majority of phenotypic traits of hybrid F1 presented intermediate values,(b)the pollen viability of interspecific hybrid F1(6.58%)was less than that of female(97.08%)and male(94.51%),and(c)analysis of SSR markers clearly indicated that interspecific hybrid F1 had bands from the paternal and maternal accessions,which confirmed that F1 hybrid was authenticity.Here,interspecific hybrids between C.annuum and C.chacoense will not only expand genetic diversity of cultivated pepper,but also provide the basis for transferring excellent genes from C.chacoense into cultivate pepper. |
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