Distribution,Diversity And Evolution Of Cucurbit Viruses In China

The Cucurbitaceae family(cucurbita)contains important economic crops in China.More than 28 viruses that infect and damage cucurbit crops,leading to nearly a loss of 30 billion RMB each year in China.With the global climate warming,and international trade encrease,the expansion of planting regions and the diversification of planting patterns,the number of viral diseases infecting cucurbit crops has also increased year by year.This study investigated the occurrence of viral diseases in the main producing areas of watermelon and melon in China.Samples with viral disease symptoms,collected from difference region,were used for identification of virus by next –generation sequencing technology and routine detection methods.Two emerging viruses belonging to genus potyvirus in cucurbit and one novel virus belong to genus polerovirus were identified.Phylogeny analysis using single nucleotide polymorphism was performed for the four pervasive cucurbit viruses in China.The main results are as follows:(1)The specises and distribution of cucurbitaceae virus in China were determined.The occurrence of viral diseases was investigated on watermelon and melon in 9 provinces,31 districts and counties,52 planting plots in winter-producing areas of South China,production areas in the south of the Yangtze River,Central China,Southwest of China as well as Northwest.A total of 288 suspected virus samples were collected,including 109 samples from watermelon,95 from melon,57 from pumpkins,and 27 from other cucurbit crops.The results of small RNA sequencing and de-ribosomal RNA sequencing were used to detect and identify virus.Twenty-two viruses from 12 genera were detected by NGS technology and conventional detection technology,among,which,21 were well-documented virus and one was newly discovered virus species.According to the classification of viral nucleic acid types,positive single-stranded RNA viruses was dominant type;according to the classification of virus gene,potyvirus was dominant;according to the classification of virus species,zucchini yellow mosaic virus was dominant;according to the classification of virus transmission mode,the aphid transmission method was dominant;according to the classification of the number of viruses infecting a single sample: the number of single virus infection samples was dominated.The types and distribution of viruses infected different Cucurbitaceae crops were compared and analyzed.The occurrence and distribution of viruses in different planting areas were compared and analyzed.The obvious difference was that thethrips-transmitted viruses in southern China was dominant,while the other areas were dominated by aphid transmission viruses.(2)The genomic characteristic and biology of zucchini tigre mosaic virus and papaya leaf distortion mosaic virus were determined.Based on the results of NGS and RT-PCR,the complete gemomic sequence and genomic characteristics of zucchini tiger mosaic virus(ZTMV)and Papaya leaf deistortion mosaic virus(PLDMV)were determined.ZTMV was a recombinant virus and PLDMV has a low genome sequence identity to other strain reported virues in papaya.The infective clones of ZTMV and PLDMV were successfully constructed by the recombinant fusion method.Purified viral material of three isolates in two viruses was obtained from a variety of virus complex infection samples to verify its infectivity and transmission ability.The host range of the four isolates in two viruses and the sympotm on different cucurbitaceae crops were determined.(3)A novel virus belongs to the genus polerovirus,was identified.We report a novel member of the genus Polerovirus,zucchini aphid-borne yellows virus(ZABYV),which was identified from zucchini consumed for seeds in Xinjiang Uygur Autonomous Region,China.The complete nucleotide sequence of the ZABYV genome was determined,which is 5,792 nucleotides in length and same as other poleroviruses,contains seven open reading frames(ORFs).Multiple sequence alignments and phylogenetic analyses indicate that ZABYV is a new member of the genus Polerovirus.Further comparative analysis suggests that ZABYV could be derived from a recombinant event between CpCSV and another unknown virus in the genus Polerovirus.(4)The characteristics of phylogeny of the pervasive four cucurbit viruses were identified and some phylogenetic group were discovered.The approximate full-length genomic sequences,obtained from NGS data,were used for the phylogenetic analysis of the four viruses.the genetic diversity of the cucumber mosaic virus in this study was narrow,all belong to subgroup Ⅰ B;Suspected reassortment events were found among some isolates of CMV.The population of ZYMV in this study have a diverse genetic background.A novel group of ZYMV,distinguished from other ZYMV isolates reported,were discovered and a hypothesis of correlation between phylogeny and location of ZYMV population was proposed.The phylogenetic groups of WMV population were defined based on complete genomic sequence.A new group of PRSV population was defined based on complete genomic sequence and the correlation between phylogeny and host and location of PRSV was discussed.SNPs in genome of the four viruses population were identified using a bioinformation pipeline based on the NGS data.In this study,approximately 300 samples were collected form plants showing the viral disease symptom in melon and watermelon fields in China.The type and distribution of cucurbit viruses were determind by NGS combining routine methods.The characteristics of two emerging viruses and a novel virus were described.The phylogenetic characteristic of pervasive four cucurbit viruses were identified and novel groups were discovered.These results improved our understanding of the incidence and distribution of cucurbit viruses in China and will be useful to control the incidence of viral diseases worldwide.