Identification And Population Dynamic Of Parasitic Nematodes In Died Pine Trees Infested With Bursaphelenchus Xylophilus

The pine wilt disease or called Pine wilt disease, is the causal agent of pine wilt disease inEast Asia and destroys millions of pine trees every year. For a long time, Bursaphelenchusxylophilus ([Steiner&Bubrer1934)Nickle1970] is seemed to the main pathogen of the disease.However,in recent years, lots of unexplained and different Symptom of dead pines were found in ourcountry. In these trees B. xylophilus was difficult to be detected, whereas, abundant of B.mucronatus or other parasitic nematodes were found. Due to various pine parasitic nematodesand some problems of pathogenicity, biology and relationship with the host are not clear,anation-wide survey for the identification and population dynamic of parasitic nematodes in thedying pine trees infested with B. xylophilus was conducted in China. From which we could learnmuch about the variation of populations of parasitic nematodes and the competitive interactionbetween B. xylophilus and presence of dominant nematodes in the dying pine trees. It mightreveal the internal relations between a multitude of phenomenon of the died pine and pineparasitic nematodes. In addition, it also can provide some guides for integrated management ofthe pine wilt disease. The results achieved are as follows:1. Sixteen species(including two species indeterminata)were found from354nation-widesamples and they belonged to five genera and four family based on morphological identification.Among them one was new records from China. They were Cylindrotylenchus pini,Cryptaphelenchoides propora, Ektaphelenchus compsi, Ektaphelenchus pini, Seinura tritica,Bursaphelenchus xylophilus, B. mucronatus, B. thailandae, B. aberrans, B. rainulfi, B. minutus,Aphelenchoides bicaudatus, Aphelenchoides daliannensis, Aphelenchoides macronucleatus,Aphelenchoides sp. and Aphelenchoidae sp.2. Population variations of these sixteen species suggested that the pine wood nematode hadthe highest rate of incidence and was the dominate species in diversities of nematodes within pinewood. Meanwhile, the host range and regional distribution of B. xylophilus was the most widely.It can endanger many kinds of pine trees and nearly distributed all provinces in this survey.However, the other parasitic nematodes can only live in one or several kinds of pine woods andtheir separation ratioes changed along with the host. The regional distribution of the otherparasitic nematodes was also confined to several provinces.3. To study the variation of populations of parasitic nematodes in natural dying pine trees,withered P. massoniana of Jiangsu Academy of Forestry was sampled. The result showed that sixparasitic nematodes were isolated from the dying pine trees in seven sampling processes, whichwere B. xylophilus, B. minutus, B. thailandae, E. comps, E. pini, B. aberrans. B. xyluphilus occupied a position of absolute dominance, its population fluctuation was large over time and thevariation trend was also inconsistent in different hostes. Normally, two to four of the othernematodes coexist with B. xylophilus, their population quantity was few and populationfluctuation was discontinuous. The result also indicated that the number of pine wood nematodeand the water content in host was really irrelevant except E. pini.4. To investigate the possible interaction between the alien invasive species B. xylophilus andB. mucronatus, B. rainulfi, B. thailandae in a fungal mat and a susceptible host. By comparingthe propagation parameters of these species under competitive and noncompetitive conditions. Itwas shown that the propagation level of B. thailandae was clearly higher than that of B.xylophilus on fungi; the propagation level of B. mucronatus and B. rainulfi was whereas clearlylower than that of B. xylophilus. Meanwhile, B. thailandae can restrained and excluded B.xylophilus when the two species were cultured as a mixture for a longer time; B. mucronatus andB. rainulfi was similarly competitively displaced by B. xylophilus. The date of mulplicity onpines noted that the competitive interaction between B. xylophilus and B. mucronatus on pineswas similar to that on fungi. Because B. rainulfi and B. thailandae can not propagate too much onpines, B. xylophilus occupied a position of absolute dominance in the competition against the twospecies. Furthermore, the influence of interspecific competition on the sex rate wasnonsignificant.