Phylogenetic Analysis Of Zucchini Yellow Mosaic Virus In Hunan Province,China

Viral diseases are among the major constraints for cucurbit production in Hunan province, China. During 2013-2015, in total 662 leaf samples from 9 cucurbit species exhibiting virus-like symptoms were collected and assessed for Zucchini yellow mosaic virus (ZYMV) infection by reverse transcription polymerase chain reaction (RT-PCR). ZYMV, was present in 54.5% of samples. As virus diversity leading to emergence of new strains is often considered a significant factor in virus epidemics, we further analysed the population diversity of Hunan ZYMV isolates with coat protein (CP) and helper component proteinase (HC-Pro). The Hunan isolates were grouped into A-II, A-III and C-II according to phylogenetic analysis of CP nucleotide (nt) sequences, while they grouped into A-I and C according to HC-Pro nt sequences. Based on phylogenetic and computational analysis, recombination event between subgroups AIII and CII in CP was detected. This is the first report of recombination in ZYMV. Neutrality tests illustrated that negative selection was the major force operating upon the CP and HC-Pro genes of ZYMV, although one positively selected site was detected for CP encoded proteins. On the meanwhile,20 sites in the CP and 20 sites in the HC-Pro were accepted as negatively selected sites, respectively. These results delineate composition of the ZYMV population in Hunan province, China, and also suggest that recombination among strain subgroups does occur for the first time.