First Report of Tobacco mosaic virus in Abutilon theophrasti in China.

Velvetleaf (Abutilon theophrasti Medic), a tall, fecund, self-fertile annual plant in the family Malvaceae, is widely grown in China as a fiber crop and for its medicinal properties. In July of 2008, we observed diffuse chlorotic and necrotic spots on the oldest leaves of velvetleaf plants in the field in Shanxi Province. Sap extracts from six symptomatic plants were tested by direct antigen coated ELISA using polyclonal antibodies specific to Potato virus Y (PVY) and monoclonal antibodies specific to Tomato mosaic virus (ToMV), Cucumber mosaic virus (CMV), and Tobacco mosaic virus (TMV). Five of the six samples were negative for ToMV, CMV, and PVY but positive for TMV. Double-stranded RNA extracted from leaves of the five velvetleaf plants was used as template for reverse transcription (RT)-PCR as described by Krajačića et al. (1) and Li et al. (2) with some modifications. One-step RT-PCR was performed using a Quant One Step RT-PCR Kit (TIANGEN BIOTECH CO., LTD., Beijing, China) with sense (5'-CTGTTTAGCCGGTTTGGT-3'), and antisense (5'-TCCCTTTACGGACATCAC-3') primers (3) designed to specifically amplify a fragment of the movement protein coding region of TMV. The expected 470-bp fragments were amplified from dsRNA from these five plants and the amplicon from each plant was cloned and sequenced (GenBank Accession No. FJ873800). Comparisons of a consensus sequence derived from the five amplicons with the nucleotide sequences available in the NCBI database using BLAST showed 99% identity with TMV from South Korea (GenBank Accession No. AB354955) and Spain (Accession No. AJ308692) and 98% with TMV from China (Accession No. AF165190). The serological, RT-PCR results and sequence data revealed that these velvetleaf plants were infected by TMV. On the basis of the serological analysis and genome sequence comparisons, this isolate was tentatively designated as TMV-Velvetleaf. To our knowledge, this is the first report of TMV in Abutilon theophrasti Medic in China. References: (1) M. Krajačić et al. J. Chromatogr A. 1144:111, 2007. (2) H. Li et al. Agric. Sci. Chin. 6:86, 2007. (3) Y. B. Niu et al. Chin. Biotechnol. 29:76, 2009.