An isolated population of heterobasidion abietinum on abies pinsapo in spain

Abies pinsapo, a fir endemic to a small area in southernmost Spain, is frequently attacked in natural stands by Heterobasidion root rot. To identify the Heterobasidion species causing the disease, pure cultures of the fungus were isolated from symptomatic trees in five localities in Sierra de las Nieves Natural Park and identified by pairing tests. In addition, genets of the fungus were identified in two pure stands of A. pinsapo. All the Heterobasidion specimens collected belonged to the species Heterobasidion abietinum. The largest genet found was 57 m long, and had colonized 10 trees. The large size of the main genets implied that H. abietinum had spread via root contacts from old infections generated before the establishment of the Sierra de las Nieves National Park in 1989. Exceptionally dry summers in the last 20 years may have weakened A. pinsapo and favoured spread of the disease.