During the 2004 growing season in the Liaoning Province in China, where there was large population of whiteflies, several sweet potato (Ipomoea batatas) breeding lines showed leaf curl symptoms. A survey was conducted to determine the incidence of Sweet potato leaf curl virus (SPLCV) in China. Sixteen plants were collected and stem scions from those plants were graft inoculated to Ipomoea nil. Three weeks later, the indicator developed symptoms of leaf curling, interveinal chlorosis, and stunting. Total nucleic acid was extracted from young leaves of sweet potato and then evaluated using polymerase chain reaction (PCR). Primers, developed by Briddon and Markham (1) and used as universal primers for amplification of the geminivirus DNA fragment, were BM-V (5′-KSG GGT CGA CGT CAT CAA TGA CGT TRT AC-3′) and BM-C (5′-AAR GAA TTC ATK GGG GCC CAR ARR GAC TGG C-3′). Amplified fragments with BM primers theoretically should have sizes almost equal to the full length of the DNA A component of the bipartite genome (2). Expected DNA fragments of 2.8 kb that contained the AV1, AV2, AC1, AC2, AC3, and AC4 open reading frames were obtained from symptomatic, but not from symptomless (uninfected) plants. The 2.8-kb fragments obtained by amplification were purified and cloned into the PMD18-T vector. Recombinant plasmids were then transformed into competent cells of Escherichia coli strain DH5(. The fragment was sequenced (GenBank Accession No. DQ512731), and nucleotide sequence of corresponding regions were compared with a published sequence of SPLCV available in GenBank (Accession No. AF104036). The AC4 and AC2 genes showed the highest (92%) and the lowest (83%) identity, respectively. This virus has been reported in the United States, Taiwan, Japan, and Peru. To our knowledge, this is the first report of the natural occurrence of SPLCV in China.
References: (1) R. W. Briddon and P. G. Markham. Mol. Biotechnol. 1:202, 1994. (2) M. Onuki and K. Hanada. Ann. Phytopathol. Soc. Jpn. 64:116, 1998.
