The Genetic Diversity And Tree Distribution Research Of 'Candidatus Liberibacter Asiaticus',One Species Of Citrus Huanglongbing In Ganzhou Region

Citrus Huanglongbing(HLB),namely yellow shoot disease or greening disease,was widely spreaded in citrus production areas in south of China,Southeast Asia,Africa,Brazil,the United States.It is a tremendous threat to world citrus industry.Typical HLB feature includes blotchy-mottled yellow leaf,lopsided fruit,green soft fruit or "red nose fruit",causing economic losses,even trees' debilitating or death.For the moment,the cultivation of the pathogen and Koch's postulates have not been completed.However,according to the 16 S rDNA gene,geographical origin and thermal sensibility,the pathogen was scheduled for alpha deformation bacterial phyla Liberibacter belonged to three species: ?Candidatus Liberibacter asiaticus?(CLas),?Candidatus Liberibacter africanus?(CLaf),?Candidatus Liberibacter americanus?(CLam),?Candidatus Liberibacter africanus subsp.capensis?,and currently Chinese citrus were harmed by CLas the most widely and severely.It wasn't confirmed when HLB happened in Ganzhou area,while HLB disease outbreak in Ganzhou in 2013,seriously impacting Ganzhou citrus industry brand development,such as Gannan navel orange,Nankang pomelo,Xunwu tangerine.This paper carried out research among the following several aspects: 1.Collecting 516 HLB samples from different geographical origins in Ganzhou area,using Multiple-Locus Variable number tandem repeat Analysis(MLVA)to carry out the genetic differentiation in Ganzhou;2.Using relative quantitative method(??CT)to analyse content of pathogenic bacteria distribution characteristics on Newhall Navel Orange;3.Through real-time fluorescence quantitative PCR(qPCR)compared sensitivity of HLBp,CQULAP two group TaqMan probes and SYBR green targeted nusG-rpl KAJL-rpoBC gene cluster.Then get the following conclusions.1.CLas genetic diversity in Ganzhou area is very rich.We screened out 5 locus from 23 to study Ganzhou region's diversity,finding LasSSR-A locus' genetic polymorphism is the highest,which Nei' index higher than 0.9,followed by the LasSSR-E site,which site has a lack of 20%samples in Ganzhou;based on the LasSSR-C locus,the LasSSR-D site,the site CWBJ44 of clustering analysis showed that,Dayu County samples clustered as a class,different from other counties.2.Positive rate of conventional PCR for five trunk branches was 88.57%,61.11%,54.17%,6.67% and 0,qPCR was 100%,100%,100%,40%,13%,respectively.??CT method show?Candidatus Liberibacter asiaticus? content and positive rate is higher in blotchy-mottled blades.Pathogen showed systemic infection and uneven distribution in the plant host.3.HLBp probe sensitivity is 10 times higher than CQULAP probe and SYBR green targeted nusG-rplKAJL-rpoBC gene cluster.The three methods are enough to detection in molecular laboratory,which can avoid conventional PCR prone to false negative drawbacks.