アカマツにおけるマツ材線虫病の進行と通水異常

概要

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Pinus densiflora SIEB. et ZUCC. is suscep. tible to the pine-wilt disease caused by a nematode, Bursaphelenchus xylophilus (STEINER et BUHRER) NICKLE. We inoculated P. densiflora trees with the nematode and studied the blockage of the xylem-sap ascent by tracheid cavitation (dehydration by gas), which is a very significant phenomenon involved in this disease's development. Cavitation started one week after the nematode inoculation. Cavitated areas first were observed as small spots scattered on disks from trunks (first stage of water blockage). After that, came an increase in spot numbers (second stage) and an enlargement of the cavitated areas (third stage), all stages being much slower in the case of P. thunbergii PARL. Six weeks after inoculation, xylem desiccation and cambial necrosis had progressed (last stage). Volatile terpenes inreased in the xylems from one week after inoculation, but in some cases, the increasing rate was much less than that in P. thunbergii. We concluded that nematode-infected P. densiflora also dies from extensive water-deficits due to water blockage by tracheid cavitation. Slightly greater resistivity of this species, when compared with P. thunbergii, will come from the slower development of cavitation.
1991-01-01