Raffaelea quercivora (Japanese oak wilt).

Raffaelea quercivora, together with ambrosia beetle Platypus quercivorus as a vector, is the causal agent of Japanese oak wilt. P. quercivorus occurs from south to east Asia, including Japan, and is associated with trees in the Fagaceae family. R. quercivora is considered native to Japan, Taiwan, Indonesia, Thailand and Vietnam. In Japan, Quercus serrata and Q. crispula [Q. mongolica] are particularly susceptible to Japanese oak wilt, with high rates of mortality. Although there have been reports of the co-occurrence of R. quercivora and P. quercivorus outside of Japan, tree mortality caused by this species complex has never been recorded in these cases. R. quercivora is not on an alert list or listed as a regulated pest in any part of its native range. Although R. quercivora/P. quercivorus are not considered invasive, if they were introduced into susceptible oak forests, possibly via international transport of wood products, there is potential for them to cause extensive tree mortality in other geographic regions.

Raffaelea quercivora (Japanese oak wilt).

Raffaelea quercivora, together with ambrosia beetle Platypus quercivorus as a vector, is the causal agent of Japanese oak wilt. P. quercivorus occurs from south to east Asia, including Japan, and is associated with trees in the Fagaceae family. R. quercivora is considered native to Japan, Taiwan, Indonesia, Thailand and Vietnam. In Japan, Quercus serrata and Q. crispula [Q. mongolica] are particularly susceptible to Japanese oak wilt, with high rates of mortality. Although there have been reports of the co-occurrence of R. quercivora and P. quercivorus outside of Japan, tree mortality caused by this species complex has never been recorded in these cases. R. quercivora is not on an alert list or listed as a regulated pest in any part of its native range. Although R. quercivora/P. quercivorus are not considered invasive, if they were introduced into susceptible oak forests, possibly via international transport of wood products, there is potential for them to cause extensive tree mortality in other geographic regions.

Draft Genome Sequence of Raffaelea quercivora JCM 11526, a Japanese Oak Wilt Pathogen Associated with the Platypodid Beetle, Platypus quercivorus

The Japanese oak wilt pathogen Raffaelea quercivora and the platypodid beetle, Platypus quercivorus , cause serious mass mortality of Quercus spp. in Japan. Here, we present the first draft genome sequence of R. quercivora JCM 11526 to increase our understanding of the mechanism of pathogenicity and symbiosis with the ambrosia beetle.

Comparison of Sapwood Discoloration in Fagaceae Trees After Inoculation with Isolates of Raffaelea quercivora, Cause of Mass Mortality of Japanese Oak Trees

The mass mortality of oak trees has been prevalent in Japan since the late 1980s. The fungus Raffaelea quercivora is transmitted by an ambrosia beetle, Platypus quercivorus, which causes mortality. The beetle is able to bore galleries into the sapwood of most Fagaceae trees in Japan; however, the level of mortality caused by R. quercivora and P. quercivorus differs greatly among tree species. Previous studies by our research group have demonstrated that the virulence of R. quercivora differs among isolates when inoculated into Quercus serrata logs. However, interactions between the virulence of R. quercivora isolates and the susceptibility of other fagaceous species have yet to be elucidated. In this study, we inoculated the fresh logs of 11 fagaceous species with isolates of low and high virulence, and measured the tangential widths of discolored sapwoods 3 weeks after inoculation. Although the discoloration widths of Q. crispula sapwood were similar among all isolates, those of Q. serrata and Q. acutissima tended to increase with the more virulent isolates. Sapwood discoloration in Q. glauca, Q. acuta, Q. salicina, Lethocarpus edulis, and Castanopsis sieboldii was greatly increased by highly virulent isolates. Discoloration in Fagus japonica was not influenced by any of the isolates. The logs of Q. crispula and Q. serrata but not Q. glauca were significantly more discolored by a low-virulence isolate compared with standing trees. The various virulent isolates induced unique sapwood discoloration characteristics in each species, which may explain species-specific differences in mortality rates.

A New Cytosporone Derivative from the Endophytic Fungus Cytospora sp

Japanese oak wilt (JOW) is a tree disease caused by the fungus Raffaelea quercivora, which is vectored by the ambrosia beetle, Platypus quercivorus. In a screening study of the inhibitory active compounds from fungi, a new cytosporone analogue, compound 1, was isolated from the endophytic fungus Cytospora sp. TT-10 isolated from Japanese oak, together with the known compounds, integracin A (2), cytosporones N (3) and A (4). Their structures were determined by extensive 1D– and 2D–NMR spectroscopic and mass spectral analyses. Compound 1 was identified as 4,5-dihydroxy-3-heptylphthalide and named cytosporone E. Compounds 2 and 3 showed antimicrobial activity against Raffaelea quercivora.