The Interaction Between Papaya Ringspot Virus And Papaya Leaf Distortion Mosaic Virus In Papaya

Papaya is one of the important tropical fruits and vegetables in Hainan.Papaya ringspot virus(PRSV)and papaya leaf distortion mosaic virus(PLDMV)are the important limiting factors for the papaya industry.In recent years,mixed infection of PRSV and PLDMV was found and this phenomenon incidence increased year by year.It is considered to become a new threat limiting factor for the papaya industry.Therefore,it must make a thorough study of mixed infections machine.Research and access to research results of this study were as follows:1.Nucleotide sequence and amino acid sequence analysis of sample mixed infections with PRSV and PLDMV:Two full-length cDNAs,named as PRSV-LM and PLDMV-LM,were cloned from mixed infection(which collected from Lingshui,Hainan)by using RT-PCR and rapid-amplification of cDNA ends(RACE)techniques.The full-length genome of the two viruses were 1,0325 bp and 1,0153 bp(not including the 3’ end of a polyA)by sequencing.Sequence analysis indicated that,the full-length nucleotide sequences and amino acid sequences similarity were 94%,between PRSV-LM and PRSV single infection isolate Hainan-DF(GenBank accession number:EF183499).The full-length nucleotide sequences and amino acid sequences similarity were 99%and 97%,between PLDMV-LM and PLDMV single infection isolate Hainan-DF(GenBank accession number:JX974555).2.Study of PRSV and PLDMV single infection:In this study,we successfully constructed PRSV-LM and PLDMV-LM infectious clone which applied Agrobacterium inoculation by yeast homologous recombination system.Finally we obtained PRSV-LM infectious clones and PLDMV-LM infectious clones can be infected.Compared the symptoms of PRSV-LM with PLDMV-LM,revealing that PRSV-LM was more destructive than PLDMV-LM.After sequencing we found that,PRSV-LM genomic sequence at nucleotide 1825 A mutated to G,but it still corresponding to amino acid threonine.PLDMV-LM genome sequence did not mutated.3.Studies of interaction between PRSV and PLDMV:In order to evaluate the infectious potential of mixed infection,simultaneously and asynchronous inoculation tests in Non-transgenic variety of papaya Solo.The multiplicative fluctuation of virus quantitatively monitored by RT-PCR and real-time RT-PCR.The results showed that the symptoms of mixed infection between two viral single infection.After inoculation 3 weeks,all the treatments showed that the amount of PRSV-LM accumulation is greater than the amount of PLDMV-LM accumulation.The results showed that PRSV-LM steady reached the maximan amount with 107 to 108 copy numbers and PLDMV-LM fluctuated between 103 and 108 copy numbers.The simultaneously inoculation results showed that,PLDMV-LM accumulation between 103 and 105 copy numbers.The accumulated amount of PRSV-LM was higher than the PLDMV-LM.Asynchronous inoculation tests showed that inoculation PLDMV-LM after inoculation PRSV-LM has the same result with the simultaneously inoculation.It also showed that powerful infection ability Strain PRSV-LM has dominant position in the competition for space and nutrients.Conversely,inoculation PLDMV-LM before PRSV-LM,PLDMV-LM has comparative advantage at the beginning.It seemed that PLDMV-LM showed similar cross-protection role for PRSV-LM.The accumulation amount of PRSV-LM would exceed PLDMV-LM later.Finally,they can co-exist in a papaya.The reason for this situation need to be further studied.In conclusion,there may be a certain competitive interaction between PRSV-LM and PLDMV-LM,finally they can co-exist in a field.The results can be used to speculate the possible evolution of the mixed infections in the filed.And It also used as a reference for breeding and disease resistance.