Abstract:

By inoculating pine (Pinus thunbergii) seedlings with pine wood nematode (Bursaphelenchus xylophilus), the death course and manner of host parenchymatous cells in pine wilt disease were studied. Programmed cell death (PCD) was observed with fluorescence micrographic technique in parenchymatous cells of host cortex in succession after being inoculated. It appeared typical apoptosis characters as follows. Chromatin became condensated and margination looked like the shape of crescent. The nuclei were distorted, and exhibited irregular fragmentation until eventually degenerated. All of these cell apoptosis phenomena took place not only near the inoculated dot, but also in the tissues where the nematodes did not reach. The quantity and degree of the cell apoptosis increased gradually and nematode spread over after infection with the time. This paper for the first time proposed that the PCD took place in infected pine host and provided cytology evidence that B. xylophilus was able to induce PCD in infected host pine parenchymatous cells. PI(propidium iodide) fluorescence dyeing technique was for the first time applied in plant PCD research. This study suggests that PI fluorescence dyeing technique would be a useful method in plant PCD study.

Key words: pine wilt disease, programmed cell death (PCD), PI(propidum iodide) fluorescence dyeing