The basidiomycete Heterobasidion annosum (Fr.:Fr.) Bref. is a pathogen of conifers in the Northern Hemisphere. This fungus has been previously reported from Pinus spp. (1) and from Abies religiosa (H.B.K.) Schl. et Cham. (2) in Central Mexico. In 1998, H. annosum was collected for the first time from stumps of Abies hickeli Flous et Gaussen in the Southern Mexican State of Oaxaca, at an altitude of 2,900 m (Lat 17° 28′ N, Long 96° 31′ W). Although standing trees at the sampled site were asymptomatic, the sapwood and heartwood of several fir stumps were extensively decayed. The white laminated rot was similar to that caused by H. annosum on other Abies spp. Decay pockets extended to the upper surface of the stumps, indicating the fungus had infected and colonized the tree butts prior to tree felling. H. annosum basidiocarps were found both outside the roots in the duff layer and inside the decay pockets. The anamorph of H. annosum (Spiniger meineckellum (A. Olson) Stalpers) was isolated from the context of three basidiocarps. Based on comparative analysis of DNA sequences of the nuclear ribosomal internal transcribed spacer region, all three isolates belonged to the North American S intersterility group (ISG). This report expands the host and the geographic ranges of the North American S ISG, and represents the world's southernmost finding of an Abies species infected by this pathogen.
References: (1) R. Martinez Barrera and R. Sanchez Ramirez. Ciencia Forestal 5(26):3, 1980. (2) M. Ruiz-Rodriguez and L. M. Pinzon-Picaseno. Bol. Soc. Bot. Mexico 54:225, 1994.
