First Report of Tomato yellow leaf curl virus in Viola prionantha in China

Tomato yellow leaf curl virus (TYLCV) is a member of the genus Begomovirus, family Geminiviridae. Following the first identification of TYLCV in Shanghai, China in 2006 (Wu et al. 2006), it has been reported from many provinces of China as one of the most important tomato pathogens. TYLCV is transmitted by whitefly Bemisia tabaci, while weed plants act as intermediate hosts and play an important part in the emergence of TYLCV (Papayiannis et al. 2011; García-Andrés et al. 2006). Viola prionantha, family Violaceae, is a common weed grown in the field. It has a wide geographic distribution and can be found in courtyards, gardens, and orchards. Twenty-five symptomless samples of V. prionantha were collected near a tomato greenhouse in Haidian District, Beijing, where 70% of tomato plants displayed typical symptoms of TYLCV, and which was heavily infested with Bemisia tabaci. Total DNA was extracted from V. prionantha plants using the DNA Purification Kit (TAKARA, Dalian, China). PCR was conducted using degenerate primers PA and PB corresponding to the AV2 gene of DNA-A and part of the adjacent intergenic region (Li et al. 2004). A PCR product of approximately 500 bp was amplified from five of 25 samples. These PCR products were purified and sequenced directly, and BLASTn analysis of the sequences against the GenBank database showed high sequence identity with other TYLCV isolates. The complete DNA-A sequence was obtained using two primer pairs, SSF1 (GATTGCAGAGGAAGATAGT)/SSR1 (TCATTTCAACATGCCTCGT) and SSF6 (TAGAGAGAGAACAATTGGG)/‌SSR6 (ACTATCTTCCTCTGCAATC). The full length of the DNA-A was 2,781 bp (GenBank Accession No. KP335046) and shared 99.8% identity with KC999847, a tomato isolate from Shandong Province, China, which belonged to TYLCV-IL. TYLCV was inoculated to healthy plants V. prionantha using viruliferous B. tabaci whiteflies with a one-month inoculation access period (IAP). TYLCV was detected in six out of nine V. prionantha plants after a one-month IAP. TYLCV is still spreading throughout China, and TYLCV-infected weed plants became one of the important factors facilitating its persistence and rapid spread by whiteflies. TYLCV-infected V. prionantha plants were asymptomatic, and did not display typical symptoms like leaf curl and plant stunting. Therefore, it is important to manage this weed host in disease control. To our knowledge, this is the first report of V. prionantha naturally infected by TYLCV in China. © 2016 The American Phytopathological Society.