The mechanism of disease development in pine wilt

与日本赤松（Pinus densiflora）和黑松(P.；经鉴定，接种松材线虫（Bursaphelenchus xylophilus）后的松材属多酚类物质。一种类似儿茶素的物质是与大量木芽菌相关的最丰富的多酚类物质。单宁单体儿茶素（Catechin）对嗜木芽孢杆菌（B. xylophilus）及其相对非致病性物种mucronatus的繁殖有不利影响。在大田种植的松材幼苗中，接种了嗜木芽孢杆菌后，单宁含量明显增加，从而抵抗松材线虫的入侵。对接种松材线虫的黑松盆栽苗，每天浇水或每隔4天浇水，测定其含水量、单宁量、蒸腾速率和线虫分布。多元回归分析显示负相关。木材组织含水量与特定茎段线虫数量之间的关系，表明两者之间存在重要的因果关系。在接下来的实验中，分别在接种后7、7和14天，观察到线虫数量与(i)氧化脂质、（ii）单宁和（iii）渗滤液的数量呈显著正相关。接种14 d后，渗滤液量与单宁含量也呈显著正相关。由此得出以下假设：超氧阴离子的产生或单宁的过度积累，或两者兼而有之，都可能引起实质细胞异常物质的渗漏，这些物质堵塞管胞，从而引起宿主萎蔫。

Substances associated with tissue browning of Japanese red(Pinus densiflora)and black pine(P. -thunbergii)inoculated with pinewood nematode(Bursaphelenchus xylophilus)were identified to be some kind of polyphenolics. A catechin-like substance was the most abundant polyphenolic associated with large numbers of B. xylophilus. Catechin, a tannin monomer was detrimental to the reproduction of B. xylophilus and its relative non-pathogenic species, B. mucronatus. Tannin increased conspicuously in field-planted seedlings when they were inoculated with B. xylophilus, thereby they seem to resist pinewood nematode invasion.Water content, amount of tannin, transpiration rate and nematode distribution were determined for pinewood nematode-inoculated, potted seedlings of Japanese black pine which were watered daily or every-fourth day. Multiple regression analysis revealed negative correlations. between water content of wood tissue and nematode numbers in specific stem segment, suggesting an important causal relation between these two factors. In the following experiment, a significant positive correlation was observed between nematode numbers and amounts of(i)oxidized lipids, (ii)tannin and(iii)leachates at 7, 7 and 14 days after inoculation, respectively. There was also a significant positive correlation between the amounts of leachates and tannin 14 days after inoculation. The results bring us the following hypothesis that generation of super oxide anion or hyperaccumulation of tannin, or both may cause leakage of abnormal substances from parenchyma cells, and the substances plug tracheids, thereby causes host wilting.