| Summary: | 碩士 === 中興大學 === 植物病理學系所 === 95 === Mosaic, leaf curl, and puckering symptoms were observed in Cucumis melo L. var. Silver Light plants in the field during 2007 spring season. Three samples were collected from symptomatic plants. A virus culture SL-1 was isolated and established in the systemic hosts, Nicotiana benthamiana and C. melo L. plants via mechanical inoculation. Viral DNA was extracted from diseased oriental melon plants with leaf curl from field and polymerase chain reaction (PCR) with reported primers was used to detect the presence of begomoviral DNA-A, DNA-B, and associated satellite DNA. Begomoviral DNA-A and DNA-B were detected in all three diseased samples. The PCR-amplified 1.5 kb viral DNA-A and 2.5 kb DNA-B from one positive sample were cloned and sequenced. Base on the assemblled sequence, specific primers were designed for cloning the full-length DNA-A and DNA-B of the isolate SL-1, which were determined as 2739 and 2673, repectively, nucleotides (nt) in length. Sequence analyses were conducted using DNAMAN Sequence Analysis Software. The DNA-A contained the conserved nanonucleotides-TAATATTAC and eight open reading frames, including three in virus sense (AV1 to AV3) and five in virus complementary sense (AC1 to AC5). The DNA-B contained two open reading frames, including the nuclear shuttle protein in virus sense and the moving protein in the virus complementary sense. BLASTn analysis and sequence comparison with those available in the GenBank showed that isolate SL-1 has highest nucleotide identity of 97% and 93%, respectively, with the DNA-A and DNA-B of Tomato leaf curl New Delhi virus (ToLCNDV) from Thailand. Our results indicate that the virus causing leaf curl disease on oriental melon is an isolate of ToLCNDV and designated as ToLCNDV-OM (ToLCNDV-oriental melon isolate). In addition, 38 plants species from 4 families (Solanaceae, Chenopodiaceae, Cucurbitaceae, Leguminosae) were mechanically inoculated with ToLCNDV-OM for host reaction assay. Systemic symptoms were observed on plants of C. melo L., C. sativus L., Luffa aegyptiaca, Cucurbita pepo, Lagenaria siceraria, C. melo Linn, N. benthamiana, and Lycopersicum esculentum. To our knowledge, this is the first report of ToLCNDV causing a severe disease on oriental melon plants and can be transmitted through mechanical inoculation.
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