FIRST REPORT OF TOMATO SPOTTED WILT VIRUS INFECTING BALLOON FLOWER IN CHINA

Abstract

In June 2017, balloon flower (Platycodon grandiflorus) plants with leaf mottling, etiolation, and mosaic symptoms were observed in Kunming, Yunnan province of southwestern China. These symptoms were similar to those induced by tomato spotted wilt virus (TSWV) (Fisher, 2013). Suspected TSWV infected plant samples, as well as thrips (Frankliniella occidentalis) in flowers were collected. Four of six symptomatic plants were positive using TSWV test strips (Adgen Biotechnology). Total RNA was extracted from four TSWV infected plants and 15 individual thrips and analyzed by two steps RT-PCR (PrimeScript™ II 1st Strand cDNA Synthesis Kit and LA Taq, Takara). Three primer sets were used to clone the S-RNA, and five primer pairs to clone the M-RNA as overlapping fragments (Marshall et al., 2017). The expected size fragments corresponding to TSWV S-RNA and M-RNA amplification were obtained from 4/4 leaf and 10/15 thrips samples. Amplified fragments from plants and thrips were cloned using pEASY-T1 Cloning Kit, sequenced and assembled, revealing that the S (GenBank accession No. MF688996) and M (MF688997) genome segments of this isolate shared nucleotide identity of > 95% with an isolate of TSWV from China (JF960235，JF960236; Hu et al., 2011), indicating that the sampled balloon flower plants were infected with TSWV. To our knowledge, this is the first report of TSWV infecting balloon flower in China. Due to the devastating effects of TSWV and the increase of balloon flower cultivation area in southwestern China, it is necessary to implement management strategies to control this disease and avoid the introduction of the virus into new production areas.