松材线虫携带的一株细菌分离及其致病性

从患松材线虫病致死的黑松和马尾松病树组织及松褐天牛虫体中分离的松材线虫虫体上均分离到同一细菌菌株 .经致病性、革兰氏染色、菌体形态、培养性状和生理生化反应等测定 ,将致病菌株鉴定为洋葱伯克霍尔德氏菌 .ATBExpression自动鉴定仪的鉴定结果与上述结果相同 .在分离过程中该菌出现频率较高 ,说明是松材线虫携带的主要细菌 .人工接种试验结果显示 ,用无菌线虫或洋葱伯克霍尔德氏菌菌株分别接种的黑松无菌苗不发病 ,而用二者混合接种则使无菌苗迅速发生褐变和萎蔫 .林间利用 6年生黑松进行的接种试验结果证明 ,用无菌松材线虫和洋葱伯克霍尔德氏菌菌株混合接种的黑松与使用野生松材线虫接种的黑松都 10 0 %的患病 .单独用无菌松材线虫接种有 4株发病 ,6株没有发病 .其中发病黑松中不仅分离到了松材线虫 ,也分离到了细菌 ,而没有患病的 6株黑松中仅分离到少量松材线虫 .这说明在野外条件下接种的松材线虫可以通过某种途径重新获得细菌 ,导致了接种的黑松患病 .而接种后无菌松材线虫没能获得细菌的那些黑松就没有患病 ,说明单独无菌松材线虫不能使黑松患病 .这些结果说明松材线虫携带的细菌与松材线虫的致病性有关 .因此 ,可以把松材线虫病看作是线虫和细菌共同侵染引起的一种植物复合侵染病害 .在这

Isolation and pathogenicity of a bacterium strain carried by pine wood nematode

A bacterial strain was isolated from infected tissue and pine wood nematodes of Pinus thunbergii and P. massoniana trees died of pine wilt disease and the nema todes isolated from living beetles of Monochamus alternatus. Based on the mo rpho logical, physiological and biochemical characteristics, the pathogenic bacterial strains were identified as Burkholderia cepacia(Palleroni and Holmes ) Y abuu chi et al, =Pseudomonas cepacia(Burkholder ) Palleroni and Holmes]. The resu lt of identification by using ATB Expression D○R automatic bacteria id entificatio n system was the same with the one above. The isolation frequency of the species was high from those infected tissues and the beetles indicating that B. ce p acia was one of the main species carried by pine wood nematodes throughout the ir l ifetime. The results of artificial inoculation experiments showed that aseptic P. thunbergii seedlings inoculated with aseptic pine wood nematodes or the s train of B. cepacia alone were not wilted, but those inoculated with the combinati on of aseptic nematodes and the strain of B. cepacia showed rapid browning and wilti ng. Results of inoculation tests in a black pine forest of six years old indicat e d that trees inoculated with a mixture of aseptic pine wood nematodes and the s train of B. cepacia and those with wild pine wood nematodes were 100% diseas ed. Six trees inoculated with only a aseptic pine wood nematodes remained healthy, a nd four trees of the same treatment diseased. In the recovery only a small number of aseptic nematodes were found in the six trees. However, nematodes and bacteria were recovered in the four diseased trees. It indicates that aseptic pine wood n ematode can somehow regain bacteria and result in infection of the four trees. It shows that aseptic pine wood nematodes or the strain of B. cepatia along cannot induce the disease. All the results above demonstrate that B. cepacia is closely related to the pathogenicity of pine wood nematodes and there is c ertain synergism between pine wood nematodes and the bacterial strains in terms of pathogenicity. Based on those results, it is suggested that the pine wilt di sease is a disease complex involving pine wood nematodes and the pathogenic bact eria. The authors conclude that the nematode-carrying pathogenic bacterium, B . cepacia, is the main factor responsible for the rapid wilting of pine trees.