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Large numbers of Acacia cyclops trees are dying along the coastal plains of the Eastern and Western Cape Provinces of South Africa. The cause of the deaths has been attributed to a root and butt rot disease caused by the basidiomycete fungus Pseudolagarobasidium acaciicola. However, many signs (e.g. basidiomes) and symptoms reminiscent of Ganoderma root-rot disease are commonly associated with dying trees. In this study, isolates collected from basidiomes resembling species of Ganoderma, as well as from root and butt samples from 1 diseased A. cyclops trees were subjected to DNA sequencing and morphological studies to facilitate their identification. Multi-locus phylogenetic analyses and morphological characterisation revealed that three species of Ganoderma are associated with dying A. cyclops trees. These included G. destructans, a recently described species causing root-rot on trees elsewhere in South Africa. The remaining two were novel species, one of which is described here as G. dunense. The novel species is distinguished by its mucronate basidiome, laccate shiny pileus surface, duplex context and ovoid basidiospores. Only an immature specimen was available for the second species and a name was consequently not provided for it. Interestingly, only a single isolate representing P. acaciicola was recovered in this study, suggesting that further investigations are needed to ascertain the role of each of the four basidiomycetous rootrot fungi in the death of A. cyclops trees.

Trees in the Garden Route National Park (GRNP) indigenous forests in South Africa are selectively harvested for timber based on criteria that include signs and symptoms induced by wood-rotting fungi. However, virtually nothing is known regarding the identity and host associations of these macro-fungi in this natural ecosystem. Surveys were conducted in three harvesting compartments in the GRNP to investigate the taxonomic affiliation and species richness of these fungi on standing and recently harvested trees. Samples were collected from basidiomes on infected trees and tree stumps, and from diseased tissues on symptomatic trees. Phylogenetic analyses using ITS sequences characterized the isolates obtained into 26 Operational Taxonomic Units (OTUs) belonging to 17 genera after clustering the sequences at a 97% identity threshold. Ganoderma (Ganodermataceae) and Inonotus (Hymenochaetaceae) were the most species-rich genera and the Bloukrans compartment, with 22 OTUs, showed the highest species richness. A fungus (OTU1) affiliated with Ganoderma pfeifferi was the most abundant in the surveyed areas. Its predominance was also evidenced on host trees since it occurred on 15 of the 20 tree species sampled, with Olea capensis subsp. macrocarpa (Oleaceae) being the most colonized host. Given the wide variety of wood-rotting basidiomycetes revealed by this study and particularly the preponderance of species with pathogenic potential, more attention should be given to better understand their ecological role in this natural ecosystem as well as the effects of logging that may enhance their dissemination or negatively affect their diversity and the health of trees in the region. Fig. 2. Symptoms and signs observed on sampled trees in the GRNP: (a) sap exudation and basal stem rot, (b) bracket-like basidiomes of a Ganoderma species, (c) white mycelial mat under the bark of tree with basal stem rot. [Colour figure can be viewed at wileyonlinelibrary.com]

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