Archivio Journal of Plant Pathology

Abstract:

In August 2015, symptomatic pumpkin (Cucurbita moschata Duch.) plants were observed in Linyi, Shandong province, China. Plants exhibited symptoms of leaf mottling, crinkling and mosaic which appeared similar to symptoms caused by Tomato spotted wilt virus (TSWV) (Karavina et al., 2016). Twenty field samples, two symptomatic and 18 asymptomatic, were collected. A high incidence of thrips (Thrips palmi) was also observed in the field and on the sampling plants. Given the symptoms observed and the prevalence of thrips, TSWV infection was suspected. Total RNA was extracted from symptomatic and asymptomatic plants and analyzed by RT-PCR using specific primer pair TSWV-F1 (5’-CACACTAAGCAAGCACA-3’)/TSWV-R1 (5’-TCAGTCTTACAAATCATC-3’), designed for this study, corresponding to a highly conserved region including the complete nucleocapsid protein (N) gene. Fragments of the expected size (976 bp) were amplified from the symptomatic but not from the asymptomatic samples, and one of them was cloned and sequenced (KX185153). No other viruses were detected. The incidence of TSWV in the four acres pumpkin field surveyed was 0.45%. Sequence comparisons revealed that the N gene of this isolate shared the highest nucleotide identity of 99.9% with an isolate of TSWV from an asparagus lettuce sample from China (KP330473) indicating the pumpkin plants were infected with TSWV. Phylogenetic analysis showed that this isolate and other isolates from China clustered together with those from South Korea and Japan as a separate group. TSWV (genus Tospovirus, family Bunyaviridae) has an extensive host range (Cho et al., 1987) of which tomato, pepper, peanut and tobacco are common susceptible host crops. TSWV has been reported to infect tomato, tobacco and other plants (Dong et al., 2010) in China. To our knowledge, this is the first report of TSWV infecting pumpkin in China.