Analysis Of Population Evolution Characteristics Of Citrus Tristeza Virus In Jiangxi Wild Type Citrus And Cultivated Citrus

Citrus tristeza virus is the causal of citrus tristeza disease,which is one of the destructive citrus diseases.CTV infection shows weak trees,poor fruit quality and even death.So far,CTV has caused enormous economic loss to the world of citrus production areas.CTV mainly transmissed by field grafting and aphids feeding,and brown orange aphid poison efficiency is highest.CTV genome has 12 open reading frame(ORF),which can encode the CP,P13,P18,P20,P23,,HEL and other proteins.CTV strains contains many different strains and genotypes.Different host may show yellow seedings,stem pitting,quick decline different symptoms when they are infected CTV.Jiangxi province planted a lot of sweet orange and most of them are infected CTV.There are may wild citrus in Gannan areas and whether infeced CTV is unknown.This study mainly focus on investigating the probability of infection CTV for wild type citrus and cultivated citrus;use RFLP technique analysis their groups;use two types of genotype primer to identify genotype;and analysing seven genetic sequence information.In order to make clear the genetic diversity for wild type citrus and cultivated citrus.The main results are as follows:1?381 samples of cultivated citrus were collected from 10 counties of ganzhou,44 samples of wild type citrus were collected from the county of congyi.Use DTBIA and RT-PCR identified122 samples of cultivated citrus infected with CTV,is about 34.02%of the total number of samples;34 samples of wild type citrus infected with CTV,is about77.3%of the total number of samples.Results showed that CTV infection rate has fallen during the huanglong disease census;wild type citrus could be infected by CTV and the disease rate is extremely high.2?RFLP technique analysis the CTV group of cultivated citrus and wild type citrus composition of positive samples,the results show that 84 samples of cultivated citrus are single CP/Hinf?RFLP groups,which is 68.85%of the total number of the samples;and most of samples are group 1 and 3,they accounted for 61.91%and 28.57%among the single CP/Hinf?RFLP groups.Mixtures CP/Hinf?RFLP group is about 31.15%;most of them is group 3 and group 6,they accounted for 68.42%among the mixtures CP/Hinf?RFLP groups.32 samples of wild type citrus showed single CP/Hinf?RFLP groups,it accounted for 94.12%among 34samples,and they are all the group 3.There are 2 samples RJ11 and AY8 are groups 4,preliminary judgment they are weak strain.Results show that the groups of wild type citrus is more single than cultivated citrus,there are many samples are mixture groups among the samples of cultivated citrus;and 3 group more popular in wild type citrus,1 and 3 groups more popular in the cultivated citrus.3?Use the primers designed by Hilf and Roy to identify the genotype of 122 samples from cultivated citrus and 34 samples from wild type citrus.Roy primers identification results showed that 10 samples containing only a genotype,the remaining 24 samples containing two or more genotypes among the 34 samples of wild type citrus.14 samples containingT30.There were 10samples combinations of mix virulent strains genotype,14samples combinations of weak strains and virulent strains genotype.Cultivated citrus has 35 samples contain one genotype,the remaining 87 samples mixing two or more genotypes,accounted for 71.31%of the total sample;There are 11 samples mixed weak and strength strains,76 samples mixed different strength strain.Hilf primers identification results showed that 1 samples is unable to identify genotype,22 samples identified as single genotype,11 samples containing two or three genotypes among wild type citrus,and also found moreVT(22)and T3(12).4 samples were composed by servere isolate,7 samples were composed by weak and servere isolate.There are15 samples have not identified genotypes,57 samples have a single genotype;50 samples contain two or more than two kinds of genotypes.There are 7 samples combinations the weak isolate,43 samples combinations the servere isolate.In total:cultivated citrus and wild type citrus both have VT,T3,T30,T36,B165 genotypes,and they contain one genotype or two to five genotypes.there are moreVT and T36 in cultivated citrus CTV isolate;the most is VT,the least isT36 in the wild type citrus.And there are more servere isolates in cultivated citrus(86%),more weak and servere isolates in wild type citrus(58.3%~63.6%).No single weak strain was found in wild and cultivated citrus CTV isolates,which were mixed with servere strains.4?122 positive samples from cultivated citrus and 34 positive samples from wild type citrus were analysed recombination of CP,P13,P18,P20,P23,POL and HEL gene sequencing.The results showed that the homology of CP,P13,P18,P20 and POL from the wild type citrus is slightly higher than cultivated citrus,genetic distance is less than the cultivated citrus.CP,P13,P18,P20 and HEL genes from wild type citrus and cultivated citrus CTV isolates that d_N/d_S values are less than 1,in the negative selection,POL and P23 gene d _N/d_S is greater than 1,under positive selection.Fu and Li's D,Fu and Li's F and Tajima's D testing found that each group of CTV without obvious population expansion in recent years.Genetic diversity Pi of Wild type citrus 6genes(CP,P13,P18,P20,P23,POL)significantly less than the cultivated citrus,the data also showed that cultivated citrus group genen flow is farer than wild type citrus with foreign cultivated citrus.Comprehensive the above description:genetic diversity of cultivated citrus is more complex than the wild type citrus.