Study On Molecular Markers Of Resistance To Bacterial Wilt In Pepper Rootstock

Bacterial wilt is one of the most popular soil borne diseases in the world,which is harmful to plants,especially in Solanaceae crops.Recent years,the development of grafting cultivation technology had played a great role in improving the yield of vegetables and preventing soil borne diseases.But stocks with resistant breeding are in short nowadays.So it is very important to breed resistant rootstocks for bacterial wilt.This study was researched on the PCR detection of Ralstonia solanacearum,and combined with artificial indoor inoculation and field inoculation method to inoculate the pepper rootstock germplasm resources.And rootstocks with different resistance to bacterial wilt were screened to do diallel cross and analysis heterosis.Then study on inheritance of resistance to bacterial wilt in pepper rootstock germplasms.Using BSA method combined with SSR and ISSR molecular marker methods to screen of molecular markers against bacterial wilt.The aim was to provide scientific basis for molecular marker assisted breeding of bacterial wilt resistance in pepper rootstock.Research results were as follows:1.Using specific primers Y2/OLI1 to detected bacterial wilt isolates which from susceptible pepper plants by PCR.The results showed that 288-bp band specific fragment was amplified,which has 99%homology sequencing with a strain of Ralstonia solanacearum called EP1(No.CP015116.1)through sequence blast analysis.It indicated that using specific primers for PCR extension could accurately andeffectively detect the pathogenic of bacterial wilt.2.The artificial indoor inoculation identification showed that among the 15 pepper rootstock germplasms,two rootstocks showed high resistant level(HR),one rootstocks showed resistant level(R),three rootstocks showed medium resistant level(MR),one rootstock showed susceptible level(S),and the others were high susceptible(HS).Results of field inoculation showed that F06,G16,D16 and D36 were resistant,medium resistant susceptible and high susceptible level to bacterial wilt respectively.And they were the same with the indoor inoculation results.What’s more,there were significant differences in resistance to bacterial wilt of different rootstocks.3.Base on the disease index,heterosis of twelve Fi combinations which were made by four different resistant rootstocks in complete dialel cross were analyzed.And two combinations showed Over-HP heterosis,accounted for 16.6%;five combinations showed Over-MP heterosis,accounted for 41.7%of tested combinations,and the other combinations showed Over-LP heterosis,accounting for 41.7%.The disease index of heterosis analysis showed that pepper rootstock resistance to bacterial wilt was complex.And the parents with the same parental resistance may be the good choice for strong resistance combinations selection.4.Using F06 and D36 as parents for crosses to get Fi and F2,combined with the analysis of incidence and disease index.The results showed that the resistance to bacterial wilt of pepper F05 was controlled by cytoplasm genes and had additive effect.5.Constructing F2 population,and combining BSA method and SSR and ISSR molecular markers,3 polymorphic primers were screened out.Only one primer UBC876 could be confirmed in the F2 population.The results showed that the marker Q76 was linkage with the resistance to bacterial wilt of pepper rootstock F05.The genetic distance was 7.30cM.