FIRST REPORT OF PAPAYA RINGSPOT VIRUS ON SNOW PEA IN CHINA

Abstract

Papaya ringspot virus (PRSV), a species of the genus Potyvirus , family Potyviridae , is a major limiting factor for papaya and cucurbits cultivation in tropical and subtropi- cal regions worldwide (Purcifull et al ., 1984). PRSV mainly infects plants in the families Caricaceae , Cucurbitaceae and Chenopodiaceae , while few isolates have been reported on other hosts (Tripathi et al ., 2008). During a survey conducted in the summer of 2015, snow peas (Pisum sativum var. sac- charatum ) showing yellow ringspot symptoms were observed in some plantations in the Sichuan province (a main snow pea production area in China). The characteristic ringspot symptoms were also observed on cucurbit plants near the fields of snow pea. Leaf samples (4) were collected from symptomatic snow pea plants and tested by Western blotting with commercial antisera (Agdia, Elkhart, IN) against PRSV. PRSV was detected in all samples tested. Total RNA was extracted from each sample using Plant Total RNA Isolation Kit (FOREGENE, China). RT-PCR was performed using a pair of PRSV coat protein (CP)-specific primers: PRSV-F (5’-TAACACACTGATGGTTTTAATC-3’) and PRSV-R (5’- ATTGCGCATACCCAGGAGAGAG-3’). Expected ampli- cons of the complete CP (861 bp) were obtained, purified, cloned into the pMD19-T vector (TaKaRa), and sequenced. The sequences were identical and designated as PRSV-SC. Nucleotide BLAST analysis revealed that PRSV-SC (Gen- Bank Accession No. KX185713) shared 96% sequence iden- tity to the CP of PRSV-W isolate CI (AY027810). Phylogenet- ic analyses of CP gene of PRSV-SC using MEGA6 software revealed that its sequence clustered into the PRSV type W clade, which is separated from the PRSV-P cluster. To our knowledge, PRSV has been described in pumpkin, luffa, wa- termelon, winter melon, zucchini, muskmelon and Siraitia grosvenorii , and this is the first report of PRSV infecting snow pea in China. Recently, we showed that PRSV could also infect bitter gourd in China (Zhu et al ., 2016). Taken all together, these data suggested that PRSV presumably has a wider range of natural hosts than previously known. This apparent expansion of the natural host range is worthy of further attention.