Genomic And Pathogenic Variation Of BaMMV/baYMV Viruses Resulting In A Yellow Mosaic Disease Of Barley

Barley yellow mosaic disease is a soil-borne virus disease caused by single or combined infection of Barley yellow mosaic virus（BaYMV）and Barley mild mosaic virus（BaMMV）,which seriously threatens the production of winter barley in Europe and East Asia.Previous studies have found that there are a large number of mutant strains in both BaYMV and BaMMV.But the research in this part was not perfect in our country.This study researched the genome and pathogenicity of BaYMV and BaMMV of China.The major results are listed as follows:1.Collecting 30 soil samples from 12 provinces（mostly diseased areas）.By planting susceptible barley to identify virus accumulation in roots and leaves,cloned 5 BaYMV genomic sequences and 3 full-length BaMMV genomic sequences.2.Sequence and phylogenetic analysis revealed that there were significant differences in the nucleotide mutation rates of the coding regions of different viral proteins,among which VPg and P2 proteins had the highest frequency of nucleotide mutations and non-synonymous amino acid mutations.In addition,comparing the BaYMV sequence of Yancheng with the virus sequence isolated from the local area 20 years ago,it was found that there were 7 amino acid site mutations in the VPg protein coding region,4 of which were located in the central region that determines the pathogenicity of the virus.3.Twenty-three barley accessions containing different resistance genes/locus（rym1-rym18）were tested in Yancheng and Yangzhou for two years.The main resistance genes rym4,rym5,and rym1/11 were found specific virulence strain infection,in which rym5 infected both BaYMV and BaMMV in Yancheng.The resistance genes rym2,rym3,e IF4E_HOR3298 and rym12 currently were resistance to the virus strains in the two places and can be used as barley disease-resistant breeding.Rym13 and rym18 were only resistant to virus strains in Yancheng and were susceptible to Yangzhou strains;rym7 and rym9 were only resistant to BaYMV strains in Yangzhou.It could be seen that the BaYMV strains in the two places are differentiated in pathogenicity.Correspondingly,a comparison of the genomes of BaYMV and BaMMV from Yancheng and Yangzhou revealed that there were13 and 9 amino acid differences in the VPg protein region,respectively.It suggested that these sites may be related to the pathogenicity of the virus.This study identified barley yellow mosaic pathogens,genome composition,and disease resistance nationwide for the first time,screening out some resistant resources to provide a basis for the layout of resistant varieties in the field and laying a foundation for exploring the pathogenic differentiation mechanism of viruses and the mechanism of virus-host interaction.