The first identification of the wood-inhabiting fungus Pleurotus tuber-regium from Madagascar with a combined approach based on morphological and molecular analyses

Purpose: Madagascar is worldwide recognized as one of the top biodiversity hotspots. Our purpose was to investigate a fungal species found in Madagascar as a sclerotial mass. Methods: A fungal sample consisting of a sclerotium was collected on a Raphia farinifera log in Antsohihy (North Madagascar) and sent to our lab for characterization. Morphological and molecular analyses were carried out and small pieces of sclerotium tissue were inoculated in agar in order to isolate mycelium. Results: light and scanning electron microscope observations of the sclerotium revealed a carpet of thick-walled hyphae whereas light microscope observations of mycelium showed nematode-trapping structures. The nrITS sequence obtained from the sclerotium was compared with the GeneBank database showing high similarity with Pleurotus tuber-regium. A phylogenetic analysis clearly revealed two clades in this species: one of mainly African origin, the other one of Asian and Australasian origin. Whether these two clades should be considered two subspecies of the same species or two distinct species, is questioned, discussed. Conclusion: This study reports the first molecular identification of Pleurotus tuber-regium from Madagascar.