Analysis Of Pathogenicity Of Different Isolates Of Cucumber Mosaic Virus And Its Seed-Borne

Cross protection is a relatively effective strategy in the prevention and control of plant virus diseases.The core steps of cross protection are involved in creation of the attenuated vaccines,host range of the vaccine and timing of the inoculation.Cucumber mosaic virus?CMV?is a member of the Cucumovirus genus in the Bromoviridae family and is a tripartite single-stranded positive-sense RNA virus.CMV is mainly transmitted by aphids in a non-persistent way,as well as by seed borne or mechanical inoculation.Due to its wide range and well-identified characteristics,CMV has great potential in creation of the attenuated vaccine for cross-protection.This study mainly dealed with the detection of CMV in seeds of5 species of plant comparation of the pathogenicity of different CMV isolates and analysis of the determinant on pathogenicity of CMV isolates on corresponding hosts.It will provid materials and data for the development and application of the attenuated vaccines based on CMV.Existence of CMV was detected from about 550 seeds of two leguminous plants and three solanaceous plants via western blot and RT-PCR.The results showed that seeds of the detected pepper,tomato and peanut did not carry CMV.Seeds of the tested eggplant carried CMV in low rate at 3.3%.Seeds of the tested cowpea carried CMV in high rate at 52.5%.It is suggested that there is a limitation in the application of attenuated vaccines for the prevention of CMV in cowpea.In addition,attenuated vaccines could be used in the other tested 4 plants for cross-protection.The pathogenicity of two CMV isolates was compared on N.benthamiana.CMV tobacco isolate(CMV_Fny)presented severe pathogenicity on N.benthamiana with severe dwarfing and crinkle and mosaic symptom on leaves.CMV peanut isolate?CMVTA-pe?showed weak pathogenicity with no obvious visual symptoms.In order to identify the determinant of different pathogenicity between two CMV isolates,different combinations of RNA 1,RNA 2and RNA 3 from two CMV isolates were used to inoculate N.benthamiana.All combinations of RNA 1 or RNA 2 of CMV_TA-peA-pe replaced by RNA 1 or RNA 2 of CMV_Fny presented severe pathogenicity.Taken together,the weak pathogenicity of CMVTA-pe on N.benthamiana was mainly determined by its RNA 1 and RNA 2,and especially the RNA 2.It is also suggested that RNA 2 could be the determinant of pathogenicity of CMV even the host range of CMV.RACE and RT-PCR were used to clone the whole genome sequence of a new CMV Osmanthus matsumuranus isolate?CMVNSG?.Sequence alignment via DNAMAN showed that the genomes of CMVNSG isolates have remarkable difference from those of other CMV isolates.RNA 1 has low homology with most isolates,at 74.18%to 78.33%,with high homology to a few isolates,at 97.82%-98.99%;RNA 2 has low homology with most isolates,at 69.10%-75.28%,with high homology to a few isolates,at 98.29%to 98.62%;RNA 3 has low homology with most isolates,at 71.49%to 72.98%,with high homology to a few isolates,at 96.93%to 98.92%.In phylogenetic trees based on RNA 1 and RNA 2,CMVNSG isolates separately formed a branch.CMVNSG isolates is a novel CMV isolates due to its special RNA1 and RNA 2.This study provided research materials and data support for the development and application of the attenuated vaccine based on CMV.