华山松大小蠹及其伴生蓝变真菌对华山松木质部危害的解剖学特征(英文)

Anatomical characteristics in xylem tissue of Pinus armandi infected by the bark beetle Dendroctonus armandi (Coleoptera:Scolytidae) and its associated blue-stain fungus Ceratocystis polonica

为揭示华山松大小蠹和伴生蓝变真菌引起秦岭华山松枯萎的机制,选择秦岭北坡沣峪林场境35年树龄的健康华山松Pinus armandi为研究对象,对接种华山松大小蠹Dendroctonus armandi及与其伴生的蓝变真菌Ceratocystis polonica引起的寄主树木木质部形态变化进行了解剖观察。结果表明:接种致病性蓝变真菌C.polonica1周后的4株华山松的木质部组织内,蓝变区域显著增加,4～6周后蓝变区域不再增加;而在接种无菌琼脂的2株对照华山松的木质部组织内,没有检测到蓝变区域。研究结果提示蓝变真菌C.polonica是致死秦岭华山松的重要病原菌,该伴生菌随华山松大小蠹入侵健康寄主华山松木质部组织,在木质部定居并分解木质部,堵塞树脂道,致使寄主华山松树脂代谢和水分代谢紊乱。该研究结果表明,虽然华山松大小蠹长期以来被认为是致死华山松的毁灭性小蠹虫,但是其共生蓝变真菌C.polonica对成熟华山松的致害作用不应该被忽视。

To understand the wilting mechanism in Pinus armandi caused by the bark beetle Dendroctonus armandi and its associated blue-stain fungus, the morphological changes in xylem tissues of Pinus armandi after inoculation with Dendroctonus armandi and its associated blue-stain fungus Ceratocystis polonica were examined based on anatomical studies of the xylem of periodically harvested trees. In a field experiment, the blue-stained sapwood area of Pinus armandi was measured in response to inoculation with C. polonica, a virulent fungal associate of the pine tree bark beetle D. armandi. Four vigorous, mature P. armandi trees （35 years old） were mass-inoculated with C. polonica at a density of four inoculations per dm^2 within a 120-cm-wide band on the lower bole. Two other trees were inoculated with sterile agar and served as controls. In four trees that had been inoculated with the fungus, bluestained sapwood area increased dramatically within the first weeks after inoculation until no blue-stained sapwood area was measurable 4 - 6 weeks after inoculation. No marked blue-stained sapwood area was recorded in the two control trees that had been inoculated with sterile agar. The results confirm the ability of C. polonica to kill mature Pinus armandi trees in the Qinling Mountains. The blue-stain fungus C. polonica is pathogenic to P. armandi in the Qinling Mountains, which can quickly inhabit in host trees, and then decompose xylem tissue, block resin ducts of xylem tissue, and cause resin and water metabolic confusion. This finding suggests that D. armandi has frequently been regarded as destructive bark beetle of P. armandi in China, but as the new symbiosis pathogenic to D. armandi, the ability of C. polonica to kill mature P. armandi trees in China can＇t be ignored.