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Study on a causal agent and mechanisms of the disease development in mass mortality of oak trees.

橡树大规模死亡的病原及发病机制研究。

基本信息

批准号：
11460070
负责人：
ITO Shin-ichiro
金额：
$ 6.08万
依托单位：
Mie University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Recently, mass mortality of oak trees has been discovered in several coastal areas along the Japan Sea ; more than fifty thousand oak trees were killed in one year. Many of the trunks of the dead trees had been attacked by ambrosia beetles, Platypus quercivorus, but the biotic and abiotic mortality factors have not yet been explained. To clarify whether a pathogenic fungus was associated with mass mortality, field and isolation tests were conducted. From isolation tests from the discolored sapwood, necrotic inner bark and gallery walls of dead and wilting trees. Raffaelea sp. was most frequently isolated from the discolored sapwoods. This fungus also isolated from body surfaces of larvae, pupae and adult of P. quercivorus and from the mycangia of females. This fungus was identified as Raffaelea quercivori sp. nov. Kubono et Ito. From inoculation tests using this fungus, Quercus mongolica var. grosseserrata and Q. serrata were killed. So it was clear that this fungus had pathogenicity to oak trees. Among the fagaceous trees, Q. mongolica var. grosseserrata was most susceptible. On the other hand, Q salicina was less susceptible. The water potential of the inoculated trees decreased rapidly and then the trees wilted and died. The xylem of inoculated trees became widely discolored and vessels in such discolored areas were non-conductive. Conductivity of the vascular system was markedly less in inoculated trees. It was clear that discoloration, cambial necrosis and xylem desiccation began for the complete blockage of sap-ascent.

最近，在日本海沿岸的几个地区发现了橡树的大量死亡；一年内有5万多棵橡树被砍伐。许多枯死树木的树干遭到了鸭嘴兽（Platypus quercivorus）的攻击，但生物和非生物死亡因素尚未得到解释。为了弄清一种致病真菌是否与大规模死亡有关，进行了现场和分离试验。通过对枯死和枯萎树木变色的边材、坏死的内皮和走廊壁的分离试验。Raffaelea sp.最常从变色的边材中分离出来。该真菌也可从槲皮虫幼虫、蛹和成虫体表以及雌虫的菌丝中分离得到。该真菌鉴定为Raffaelea quercivori sp. nov. Kubono et Ito。用该菌接种试验，可杀灭蒙古栎和锯齿栎。很明显，这种真菌对橡树有致病性。在蕨类乔木中，蒙古松最易感。另一方面，水杨花不太敏感。接种后的树木水势迅速下降，最终枯死。接种后的树木木质部广泛变色，变色区域的导管不导电。接种后的树的维管系统电导率明显降低。很明显，变色，形成层坏死和木质部干燥开始完全阻塞汁液上升。