Effects of inoculum density of pinewood nematode on the development of pine wilt disease in Japanese black pine seedlings pretreated with simulated acid rain |
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Authors: | E. Asai K. Futai |
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Affiliation: | 1. Laboratory of Revegetation and Grassland Development, Arid Land Research Center, Tottori University, Hamasaka, Tottori 680‐0001, Japan;2. E‐mail: pinewilt@alrc.tottori‐u.ac.jp (for correspondence);3. Laboratory of Environmental Mycoscience, Graduate School of Agriculture, Kyoto University, Sakyo‐ku, Kyoto 606‐8502, Japan |
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Abstract: | Six‐month‐old Japanese black pine seedlings (Pinus thunbergii) were exposed to simulated acid rain (SAR) at pH 3 and 2 three times a week. After treatment for 2 months, the seedlings were inoculated with a virulent isolate (S10) of the pinewood nematode (Bursaphelenchusxylophilus), at three inoculum levels (Pi = 50, 160 or 500 nematodes per seedling). In seedlings inoculated with 500 nematodes, both population growth of nematodes and disease development were accelerated by pretreatment with SAR at pH 3 or 2. In seedlings inoculated with 50 nematodes, population growth of the nematodes was suppressed and more time was needed for seedlings to die when pretreated with pH 3 SAR. This suggests that exposure to pH 3 SAR increased not only the progress of mortality, but also simultaneously enhanced the tolerance limit of the seedlings to the pinewood nematode – the critical value of physiological burden (represented as a product of time and initial nematode population) necessary to kill a seedling. Exposure to pH 2 SAR accelerated nematode reproduction in seedlings and increased seedling mortality irrespective of the number of nematodes inoculated. |
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