This study provides new information on the infection biology and pathogenicity of an important root-rot fungus, Heterobasidion annosum sensu stricto (Fr.) Bref., through a detailed examination of the vegetative spread of clonal individuals and their capacity to produce fruiting bodies on young pine seedlings. The seedlings were planted in a clear-cutting area (c. 1.2 ha in size) after a pine generation that showed slight external symptoms of Heterobasidion root rot. The first dead seedlings were found five years after planting and during a nine-year monitoring period; nearly 600 seedlings were killed by H. annosum s.s. in 48 individual disease centers. Based on pairing tests of 482 isolates, 117 different H. annosum s.s. genotypes were identified. On average, 2.9 genotypes occurred in a single disease center. The extensive secondary spread of genotypes within root systems (up to 48 pine seedlings infected by the same genotype) resulted in annually expanding disease centers. In addition, more than half of the seedlings killed by H. annosum s.s. produced perennial fruiting bodies thus providing air-borne inoculum. The risk of spore infection should be taken into account in any type of cutting operation in young pine stands. Moreover, new control measures directed towards the secondary spread of H. annosum s.s. in pine regeneration are urgently needed in order to maintain the productivity of the pine forest on infested sites.

中文翻译：

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Heterobasidion annosum ss引起苏格兰松幼苗高死亡率

本研究通过详细检查克隆个体的营养传播及其在幼虫上产生子实体的能力，提供了有关重要根腐真菌Heterobasidion annosum sensu stricto (Fr.) Bref.的感染生物学和致病性的新信息。松树苗。在松树生长后，将幼苗种植在一块空地（约 1.2 公顷），松树表现出轻微的杂根腐病的外部症状。第一批死苗是在种植五年后和九年监测期内发现的；在 48 个独立的疾病中心，近 600 株幼苗被番红花杀死。基于 482 个分离株、117 个不同的番红花的配对测试鉴定了 ss 基因型。平均而言，单个疾病中心出现 2.9 种基因型。根系内基因型的广泛二次传播（多达 48 株松树幼苗被同一基因型感染）导致疾病中心逐年扩大。此外，半数以上被番荔枝杀死的幼苗产生了多年生子实体，从而提供了空气传播的接种物。在松树幼林中进行任何类型的切割操作时都应考虑孢子感染的风险。此外，迫切需要针对H. annosum ss 在松树再生中的二次传播采取新的控制措施，以保持受侵染地点松林的生产力。