Abstract:

1-2-year-old aquacultural excised branches of Pinus massoniana were inoculated with disinfected Bursaphelenchus xylophilus(Bx), the bacterium Bacillus firmus(Bf) accompanying Bx and the mixture of Bx and Bf respectively in order to investigate the population dynamics of Bx and its accompanying bacterium in the branches. The results showed that by inoculation with the mixture of Bx and Bf, the branches were diseased, the pith of the branches browned, the process of pith browning was from inoculated branch to main branch, and from lower part to upper part in the main branch, while by inoculation with Bx or Bf singly, the branches were not diseased. By inoculation with the mixture of Bx and Bf than with Bx singly, the propagation number and moving speed of Bx in the branches were larger. The moving process of Bx in the branches were: inoculation branch→main branch→lateral branch→current shoot, and from lower part to upper part in the main branch. The process of pith browning showed no difference from the moving process of Bx in the branches, the distribution of Bx preceded the pith browning. At early stage after inoculation with the mixture of Bx and Bf than with Bx or Bf singly, the number of pathogenic bacterium detected in the branches was larger. Thus the standpoint was proposed that both bacterium and pine wood nematode was necessary pathogenic factor of pine wood nematode disease, and pith browning in lower part of the main stem of the host could be used for early diagnosis of the disease.

Key words: Pinus massoniana, Excised branch, Bursaphelenchus xylophilus, Accompanying bacterium, Population dynamics