External Symptoms And Histopathological Changes In The Pine Wilted By The Toxins Produced By The Pathogenic Bacteria

External symptoms and histopathological changes were observed in pine trees, which were inoculated with different inoculants including non-cell culturing liquid of the pathogenic bacteria carried by Bursaphelenchus xylophilus, the mixture of aseptic B. xylophilus and the pathogenic bacteria, flagellin toxins of the pathogenic bacteria, aseptic B. xylophilus and the mixture of aseptic B. xylophilus and the non-pathogenic bacteria. Comparing results above with those in P. thunbergii inoculated with wild B. xylophilus, the relationships between the toxins produced by the pathogenic bacteria carried by B. xylophilus and pine wilt disease were studied. The main results are as follows:1. External symptoms and the trend of histopathological changes of P. thunbergii inoculated with non-cell culturing liquid of the pathogenic bacteria GcM5-1A were consistent with those of trees inoculated with wild pine wood nematodes. External appearances and the ultrastructure of the trees inoculated with aseptic pine wood nematodes and those of trees treated with the mixture of aseptic pine wood nematodes and the non-pathogenic bacteria AM2C were the same as the healthy P. thunbergii.2. The time (d.) of the appearance of the symptoms of the second phase and the number of days of the whole disease process were tested by multiple comparisons between trees of P. thunbergii inoculated with non-cell culturing liquid of the pathogenic bacteria GcM5-1A and those inoculated with wild pine wood nematodes. The results showed that in the certain dose range of the toxins, the former showed the symptoms of the second phase significantly earlier than the latter. However, their differences in the number of days of the disease process were not significant. Observation of the ultrastructure with TEM indicated that the tissues near the inoculated point in the former were damaged more seriously than those in the latter. But the damages were weaker in farer tissues from the inoculated point.3. There were not the significant differences in the time (d.) of the appearance of the symptoms of the second phase between trees of P. thunbergii inoculated with the mixture of aseptic pine wood nematodes and the pathogenic bacteria GcM5-1A and those inoculated with wild pine wood nematodes. However, the disease process of the former lasted longer than that of the latter.It was concluded that the promotive effects of pine wood nematode and its carrying varied bacteria on the toxin production of the bacteria were significantly more than those of pine wood nematode and the single bacteria strain. There were complicated relationships between pine wood nematode and its carrying bacteria, between the pathogenic bacteria and the non-pathogenic bacteria, and among the pathogenic bacteria.4. Observations of symptoms and histopathological changes in the sampled trees of P. thunbergii showed that the cavities were found in the resin canals and the cambiums in the second phase, and sampled trees were not wilted all along. However, the cavities appeared in the resin canals and the cambiums in the third phase, and sampled trees of P. thunbergii were wilted and died finally. Therefore, the author proposed that the second phase was the critical...