Coexistence of Caliciopsis pinea and Fusarium circinatum on pine: interactions among fungal pathogens.

Coexistence of pathogenic fungi on the same host has been often reported in plant pathology. As regard pine trees there are several examples on needles and shoots that, in temperate regions, could be contemporary affected by different pathogens. Less frequently, different fungal species, responsible of cankers on branches and stems, have been found on the same host. Recently in Spain, in a plantation near San Sebastian de Garabandal (coord-ETRS89 383997, 4784740 UTM 30N), during a survey, it was collected a sample from a canker on a Pinus radiata affected by Fusarium circinatum (Nirenberg & O’Donnel). The pathogen, included in the A/2 Eppo list is present in Spain and Portugal on pine species causing severe mortality. A careful observation of the canker showed that the pine was infected also by Caliciopsis pinea Peck ascomycetous fungus responsible of resinous cankers on pine, reported both in Europe and North America. The P. radiata bark showed a number of perithecia of C. pinea actively producing ascospores. The pathogens was isolated, DNA extracted from the mycelium and its taxonomical position confirmed after sequencing (amplification of ribosomal DNA ITS region and Elongation Factor gene). Dual cultures of C. pinea and F. circinatum tested in petri dishes on PDA showed weak reactions, confirming their possible coexistence. According to the literature, the environmental conditions of both fungi are very similar. Since both ascomycetes produce the same symptoms on the same species of pine, care should be taken during monitoring in the forest to avoid the risk of misidentification.