Papaya ringspot virus (PRSV) is a member of the genus Potyvirus (family Potyviridae) and causes great economic losses in agriculture (Bateson et al. 2002). So far, PRSV has been reported to infect Carica papaya, Citrullus vulgaris, Cucumis sativus, Cucurbita maxima, Cucurbita pepo, Cucurbita moschata, Luffa acutangula, Trichosanthes anguina, and Siraitia grosvenorii in the southern (subtropical) Chinese provinces of Guangdong, Guangxi, Hainan, Fujian, Taiwan, and Yunnan (Huang et al. 2008; Liao et al. 2005). However, PRSV has not been detected in northern China. In August 2016, 30 to 50% zucchini (Cucurbita pepo; cv. Zaoqing No. 1) plants in two farms of ∼10 ha in Ji’nan, Shandong Province, showed mosaic and distortion on leaves and ringspot on fruits, which caused huge damage to the yield and commercial value. Twelve samples were detected with DAS-ELISA using antibody against PRSV (ADGEN, Scotland, U.K.). The absorbance values of blank, negative, and positive controls were 0.119, 0.199, and 3.099, respectively, while those for the 12 samples varied from 0.649 to 3.631, indicating that all of them were infected with PRSV. To further confirm the existence of PRSV, primers PRSV-9061-F (5′-GCTCCATATGTGTCTGAGGTTG-3′), which was identical to nucleotides (nt) 9,061 to 9,082 of PRSV isolate CI (accession no. AY027810), and PRSV-10241-R (5′-CCTCACTGTAAAATAGAAGCGG-3′), which was complementary to nt 10,241 to 10,220, was designed. Reverse transcription was conducted using HiScript II reverse transcription (Vazyme, NanJing, China) with primer PRSV10241-R. A specific fragment of ∼1.2 kb was PCR-amplified using LA Taq DNA polymerase (Takara, DaLian, China) with primers PRSV10241-R and PRSV9061-F. The products of two independent PCR were sequenced by Biosune, Shanghai, China. The sequences was 1,058 nt in length, included 143-nt nuclear inclusion b protein (NIb) coding region, 867 nt coat protein (CP) gene, and 48 nt 3′-untranslated region (UTR). BLAST analysis showed that the virus isolate (here designated as PRSV-Ji’nan, GenBank accession no. KX904879) showed an identity of 98% at nt level with Hanoi 1, a PRSV isolate from Vietnam (FN822231). In the phylogenetic tree constructed with the CP gene using software MEGA 7.0 (Kumar et al. 2016), PRSV-Ji’nan formed a close branch with isolate Hanoi 1. To our knowledge, this is the first report of PRSV naturally occurring in zucchini in a northern Chinese province with a temperate climate. These findings highlight the importance of developing a suitable strategy for controlling the spread of viral diseases of zucchini in northern China. © 2017, American Phytopathological Society. All rights reserved.
