Surveys for plant diseases caused by viruses & virus-like pathogens in Tonga & New Caledonia

Surveys for plant diseases caused by viruses & virus-like pathogens in Tonga & New Caledonia

Suva Secretariat of the Pacific Community Fiji

2006

iv, 28 pp.

982-00-0149-8

EB0208

Surveys for plant infecting virus and virus-like diseases were conducted in Tonga, on the islands of Tongatapu, ‘Eua, and parts of the Vava’u and Ha’apai groups, and in New Caledonia on the islands of Grande Terre and Lifou. Cucurbit infecting viruses were detected by enzyme linked immunosorbent assay (ELISA) in both countries. In New Caledonia, these were Zucchini yellow mosaic virus (ZYMV) in rockmelon (Cucumis melo), pumpkin (Cucurbita maxima), squash (C. maxima x Cucurbita moschata) and zucchini (Cucurbita pepo var. melopepo); Papaya ringspot virus in pumpkin,\n squash and zucchini; and Watermelon mosaic virus (WMV) in rockmelon and zucchini. In Tonga, only ZYMV was detected in squash plants at several locations. Other viruses detected by ELISA in Tonga were Cucumber mosaic virus in a Commelina diffusa sample and Tomato mosaic virus (ToMV) in tomato (Lycopersicon esculentum). New records\n were those of ZYMV and WMV in New Caledonia and of ToMV in Tonga. In Tonga, Taro bacilliform virus was detected by polymerase chain reaction (PCR) and Dasheen mosaic virus was detected by reverse transcription (RT)PCR in the aroid crop plants, kape (Alocasia macrorrhiza) and taro futuna (Xanthosoma sp). In New Caledonia, these viruses plus Taro vein chlorosis virus were detected in taro (Colocasia esculenta). In Tonga, Banana streak virus and Banana bunchy top virus were detected in banana (Musa sp.) leaf samples by real-time PCR. Phytoplasmas were detected by nested PCR in Cyanthilium cinereum (syn. Vernonia cinerea), sweet potato (Ipomoea batatas), Indian mulberry or nonu (Morinda citrifolia) in Tonga and in tomato, strawberry (Fragaria sp.), sweet potato, onion (Alium cepa), garlic (Alium sativum) and pineapple (Ananas comosus) in New Caledonia. Most phytoplasmas belonged either to the Stolbur group (16SrXII) or the ‘Candidatus Phytoplasma aurantifolia’ (16SrII) group and one belonged to the Mexican periwinkle virescence group (16SrXIII). In Tonga, no evidence was found for presence of citrus huanglongbing, previously known as greening disease, in five\n citrus trees indexed by PCR or for Tomato leaf curl virus in eight tomato plants tested using DNA probes.

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