Dispersal Of Pine Wood Nematode Inside Resistant Pine Trees And Its Response To Host Cells

Pine wilt disease caused by pine wood nematode is the most serious forest disease in the world, which induces rapid wilt of pine. It had brought great damage to forest resources, natural landscape and ecological environment in our country. Great advances in selective breeding against B.X. have been achieved to date. One-year resistant pines and Pinus thunbergii inoculated with pine wood nematode were selected to study the dispersal and distribution of the nematodes inside the stems, and variation of water potential, cells and tissues in host, which caused by pine wood nematode. Changes of cell nucleus and reasons to cells death after inoculated pine wood nematode were analyzed by PI fluorescent staining method. The main results are as follows:Quantity variation of inoculation nematodes inside stems shows that, at the beginning, the number of nematodes inside stems were less, moving-speeds of them were slow, activities of them were weak; nematodes in the resistant Pinus thunbergii mainly moved down, and the number of nematodes was obviously smaller than that in the sensitive Pinus thunbergii; while nematodes in the sensitive Pinus thunbergii moved upwards as well as downwards, and the quantity and moving-speed downwards were obviously larger than upwards. In later stage, nematodes started to propagate, strengthen the dispersal ability, which suggested that the seedlings' symptom was related to the nematode's quantity.Changes of water potential had been tested in the study and the result showed that, water potential first occur to the sensitive pine, but both the sensitive pine and the resistant one had the same trend that rose at first, then got down, and rose again finally.Variation of quantities and speeds of cells and pathological tissues seedlings was related to nematodes moving and spreading. After inoculation, parenchyma cells which were far away from the inoculation point had less apparent pathological changes, and its quantities were only a few. Pathological changes occurred on the cortex parenchyma within the 0-0.5 cm below the inoculation point of the resistant pine after inoculation for 12 hours, whereas it occurred on the sensitive ones at the same position 6 hours earlier. In addition, the cambium of the sensitive pines appeared the above changes relatively earlier. With the continuous increase of cell death inside seedlings, the longer inoculation time was, the more extensive and severe browning and death of tissue cells were. Browning and death of the cortical layer, the phloem, and the parenchyma cells of the xylem were very commonly distributed at the beginning of the symptom. The tissue browning of the resistant pine first appear to the cortical after inoculation for 72 hours, but that of the...