Survey of Some Mushroom Farms in the Greater Accra and Central Regions; their Mycological Quality Profile and the Pathogenic Role of Trichoderma Harzianum in the Production of Pleurotus Ostreatus

Abstract

The environmental and farm aerial quality as well as the mycological purity of the basic ingredients employed for mushroom production in a mushroom farm is a sine qua non for producing healthy sporophores and gaining financial profit from the capital investment made by the producer of the oyster mushroom. In this study, seven mushroom farms in the Greater Accra Region (Ogbojo, Nii-Boi Town, Lapaz, Adenta, Ashaley Botwe, Anyaa-Awoshie) and Kasoa in the Central Region (Kasoa) were selected to provide a baseline data to help prescribe appropriate practical scientific interventions to help curb the financial losses incurred by farmers. The seven farms were; E90 Mushroom Farm, Ogbojo; Kwesi-Babs Farm, Kasoa; Immaculate Gold Enterprise, Nii-Boi Town, Lapaz; Delabless Mushroom Farm, Adenta; 4E Mushroom Farm, Ogbojo/Ashaley Botwe; Edeyef Mushroom Farm, Anyaa-Awoshie and PCM Mushroom Farm, Ashaley Botwe. The following criteria of quality were used to assess the farms; a. Resident mycoflora in the fruiting bodies produced on the farms using the conventional fungal population enumeration technique on three media (PDA, OGYE and DRBC) b. Quality of the composted growth substrate (sawdust) to ascertain species diversity of resident fungi using Decimal Dilution Technique. c. Aeromycoflora in the seven cropping rooms of the farms using the Open Plate Exposure method with the view to ascertaining the most predominant fungal species. d. In order to assess the control method for the most ubiquitous green mould causing losses in the farm house, the causative fungus Trichoderma harzianum was cultured on Potato Dextrose Agar (PDA) and in Potato Dextrose Broth (PDB) amended with varying dilutions (1:1 – 1:10v/v) of the ethanol bark extract of Anthocleista nobilis and a copper fungicide, “Champion”. e. Assessment of the growth yield and Biological Efficiency (BE) of Pleurotus ostreatus cultivated on already spawned substrate bags contaminated with T. harzianum and pre-spawned uncontaminated substrate bags. f. Mineral composition and proximate analysis of fruiting bodies employing the AOAC methods. The resident mycoflora in the mushroom fruiting body was unique for each of the selected seven (7) farms. Fungi belonging to ten (10) genera and fifteen (15) species namely Aspergillus (A. alutaceus, A. candidus, A. flavus, A. fumigatus, A. terreus), Cladosporium (C. herbarum, C. macrocarpum), Fusarium oxysporium, Gliocladium sp., Penicillium (P. brevicompactum, P. citrinum), Rhizopus oryzae, Talaromyces flavus, Trichoderma harzianum, Saccharomyces spp., and Rhodotorula mucilaginosa were encountered. Aspergillus species (6) predominated over the others followed by Cladosporium (2) and Penicillium (2). Trichoderma harzianum was the most ubiquitous fungus on the fruiting bodies isolated from all the seven (7) mushroom farms.The mean fungal population in the fruiting bodies were: T. harzianum (4.13 log10CFU/g); A. flavus (3.86 log10CFU/g); A. niger (4.10 log10CFU/g); A. fumigatus (3.60 log10CFU/g); A. candidus (3.30 log10CFU/g); A. terreus (3.20 log10CFU/g); P. brevicompactum (3.5 log10CFU/g); C. herbarum (4.20 log10CFU/g); C. macrocarpum (3.78 log10CFU/g); R. oryzae (2.53 log10CFU/g); Saccharomyces spp. (4.08 log10CFU/g); F. oxysporium (3.16 log10CFU/g). The fungal flora in the composted growth substrate (sawdust) belonged to eighteen (18) species spread through ten (10) genera. Aspergillus species (A. candidus, A. flavus, A. fumigatus, A. niger). A. fumigatus predominated. Other species isolated were Cladosporium (C. herbarum, C. macrocarpum), Didymella sp. Fusarium poae, Penicillium (P. brevicompactum, P. camemberti) Rhizopus oryzae, Trichoderma harzianum, Rhodothorula mucilaginosa, Saccharomyces spp. (yeast), Verticillium fungicola and Mycelia sterilia. Again, the species encountered were common and unique for each farm visited. The aeromycoflora isolated belonged to nineteen (19) species and twelve (12) genera and was predominated by Aspergillus species (A. candidus, A. flavus, A. niger, A. oryzae, A. parasiticus) followed Penicillium (P. citrinum, P. brevicompactum), Cladosporium (C. herbarum, C. macrocarpum), Fusarium (F. oxysporium, F. poae). Single species encountered were Epicoccum nigrum, Gliocladium sp., Mycelia sterilia, Rhodotorula mucilaginosa, Rhizopus oryzae, Trichoderma harzianum, Verticllium fungicola and Saccharomyces spp. (yeast). Radial growth of T. harzianum on PDA amended with different dilutions of A. nobilis showed that growth was commensurate lowering of depression of growth with decreasing concentration of extract. The higher the concentration, the severe the depression but the mycelium of T. harzianum cultured in different concentrations of the extract of A. nobilis approximated that of the control after 10 days. In the case of the copper fungicide, ‘Champion’ only the 1:5 and 1:10 v/v dilutions approximated the control after 10 days of incubation whilst the undiluted and 1:1 v/v dilutions suppressed growth by 60-70% in 10 days. Vegetative growth of the fungus in A. nobilis and ‘Champion’ fungicide followed the trend obtained on the agar. Infection of the fruiting body reduced the elemental composition of Calcium, Copper, Iron, Potassium, Magnesium, Sodium, Phosphorus and Zinc. The proximate analysis also showed a reduction in parameters of the following: Dry matter (%), Moisture (%), Fat (%), Crude fibre (%), Crude protein (%), Total ash (%), Carbohydrate (%) and Energy (kcal/100g). The practical implication of the finding is discussed and future work suggested.