Molecular Variability Of Cucumber Mosaic Virus And Peanut Mottle Virus

Cucumber mosaic virus (CMV), the type specie of the genus Cucumovirus (the family Bromoviridae), is probably the most widespread and successful plant virus. It has extremely broad host range and could infect plants of more than 1,000 species including many economically important crops. Peanut mottle virus (PeMoV) is also a worldwide spread virus and cause severe economical losses to plants of the family Leguminosae.The main results of this study read as follows:Five CMV isolates were obtained from tobacco (Nicotiana tabacum) or petunia (Petunia hybrida) plants showing yellowing and/or mosaic symptoms from Laiwu (isolate LW), Qingzhou (isolate QZ), Rizhao (isolate RZ) and Tai'an (isolates ND1 and ND2) of Shandong Province, China. We performed phylogenetic analysis of the genome regions containing 1a, 2a, 2b, CP, and MP genes of 5 CMV isolates from China and other 28 CMV isolates available in the GenBank. The results indicated that CMV isolates could be genetically divided into three groups I, II, and III according to the genes encoding MP, CP, 1a, and 2a proteins and to the two groups according to the gene 2b. Group I could be further divided into two subgroups (IA and IB) according to the genes encoding CP, MP, 2a, and 2b proteins and to the three subgroups (IA, IB, and IC) according to the gene encoding 1a protein. Four of 5 examined Chinese CMV isolates belonged to the subgroup IB, while the remaining isolate was a natural inter-subgroup reassortant. We found that the 2b gene of CMV was under positive selection, while the other genes were under negative selection.Twenty-eight CMV isolates were detected from peanut plants showing mosaic, stripe and/or mottle symptoms in Qingdao, Shouguang, Qingzhou, Linqu, Anqiu, Tai'an, Wendeng, Dongying, Yiyuan, and Mengyin. The 3′-terminal genome sequences of RNA3 of these isolates were determined. The phylogenetic analysis results confirmed that CMV could be genetically divided into three groups I, II, and III, and Group I could be further divided into two subgroups (IA and IB). All of 28 examined CMV isolates of our research belonged to the subgroup IB. The CP gene of CMV from peanut was under negative selection and in a state of sudden expansion.Two PeMoV isolates were obtained from naturally infected peanut showing the symptoms of mosaic and mottle of Qingdao, Shandong Province. The 3′-terminal region was amplified by RT-PCR and sequenced. This is the first report of PeMoV of China on molecular level. So far, PeMoV has only been detected in Qingdao. The CP gene of PeMoV was under negative selection.