1Persimmon and Grape Research Center, National Institute of Fruit Tree Science, Akitsu, Hiroshima 729-2494, JAPAN; 2Seccao de Proteccao de Plantas, Universidade de Tras-os-Montes e Alto Douro, Apartado 202, 5001 Vila Real Codex, PORTUGAL; 3Yamanashi Fruit Tree Experimental Station, Esohara, Yamanashi 405-0043, JAPAN

Background and objectives
Grapevine corky bark (CB) disease was first reported in Japan in 1968 [1] and was detected using the indicator grapevine cultivar LN33 in 1976 [2]. Most Vitis vinifera cultivars in Japan were thought to be infected symptomlessly until recent years. However, rugose wood (RW) symptoms (pitting and/or grooving of trunk) were found on V. vinifera cv. Kyoho, Sekirei and Koshu at Yamanashi Prefecture in the last few years. Our preliminary investigations indicated that grapevine virus A (GVA) was detected by ELISA from those varieties showing RW symptoms and that the association of GVA with RW symptoms was ca. 33%. Also, Vitivirus-like particles ca. 800 nm long were isolated from cv. Sekirei showing RW symptoms and transmitted to Nicotiana occidentalis [3]. We now report the data on the characterisation of the Vitivirus-like particles.

Materials and methods
The virus used in this studies was isolated by sap inoculation from grapevine cv. Sekirei showing RW symptoms collected in Yamanashi Prefecture which showed CB reaction on LN33. Host range in herbaceous plants, stability in sap, serology and properties of purified preparation were investigated.

Results and conclusions
The virus has a very restricted herbaceous host range. N. occidentalis reacted 5-6 days after inoculation with chlorotic/necrotic lesions followed by systemic vein clearing. N. rotundifolia showed a systemic but latent infection. No infection were observed in the other plants tested, from 13 species in 3 families. Sap from diseased N. occidentalis was infective to N. occidentalis after dilution to 10-3 but not 10-4, after 10-min heating at 45*C but not 55*C, and after 6 hours at 20*C but not 12 hours. In immunoelectron microscopy tests, the virus reacted with a grapevine virus B (GVB) antiserum produced in Italy, but did not react with GVA, grapevine virus D (GVD) and grapevine leafroll associated virus 2 (GLRaV-2). In western blots of purified preparations, coat protein band with estimated molecular weight of ca. 23 kda was recognized by the antiserum to GVB. A dsRNA molecule (ca.7500nt) was isolated from leaves of virus infected N. occidentalis. Based on these results, the virus isolated from CB-affected cv. Sekirei is proved to be GVB. The association of the virus with RW disease in Japan is under investigation.

1. Tanaka S, Otake K, 1968. Ann. Phytopathol. Soc. Jpn. 34, 204.
2. Tanaka S, 1976. Ann.Phytopathol.Soc. Jpn. 42, 192-196.
3. Imada J, Asari S, 1996. Ann.Phytopathol. Soc. Jpn. 62, 672.