Mycobiota of compost, air, fruiting bodies of Pleurotus ostreatus (EM-1) and the mycotoxigenic potential of some resident Aspergillus species

Abstract

The commercial and cottage industry entrepreneurs in Ghana have cultivated edible mushrooms such as Pleurotus ostreatus with appreciable success. However, the presence of fungal competitors and potential pathogens in the substrate obstructs yield. Selected farms in Greater Accra (6) and Central Region (1) were sampled for baseline data on the resident mycobiota of the compost (Triplochiton scleroxylon ‘wawa’ sawdust), fruiting body and aeromycoflora of the cropping rooms using conventional serial dilution technique and the Plate Exposure method respectively. Twenty (20) fungal species belonging to eleven (11) genera Aspergillus, Cladosporium, Didymella, Fusarium, Mycelia, Penicillium, Rhizopus, Trichoderma, Verticillium and Saccharomyces were encountered in the compost. The total fungal populations in compost varied significantly and with the highest recorded by E90 Mushroom Farm (4.0 to 5.24 log10CFU/g) whereas 4E Farm (2.28 to 2.93 log10CFU/g) obtained the lowest population. Eighteen (18) fungal species from ten (10) genera were isolated from the fruiting body of P. ostreatus from the farms. The most predominant species were Aspergillus species followed by Cladosporium, Penicillium, Trichoderma, Rhizopus, Saccharomyces and Talaromyces. The total mycoflora population resident in the fruiting body of the mushroom was lowest for Immaculate Gold Enterprise (2.59 to 3.22 log10CFU/g) whereas PMC Mushroom Farm (4.71 to 5.34 log10CFU/g) ranked highest. Aeromycoflora analysis showed nineteen (19) different fungal species isolated from the seven farms. Findings from the present data indicate fungi isolates from cropping rooms were also isolated from fruiting bodies and the compost. Potential toxin-producing Aspergillus species (A. flavus, A. parasiticus, A. niger, A. alutaceus, A. fumigatus) were present in the compost, the fruiting body of P. ostreatus and aeromycoflora. Keywords: Mycobiota, Trichoderma harzianum, fruiting body, Pleurotus ostreatus, aeromycoflora of cropping rooms, toxin-producing Aspergillus species.