PHENOTYPIC VARIABILITY IN CULTIVARS AND WILD STRAINS OF AGARICUS BRASILIENSIS AND AGARICUS SUBRUFESCENS

In recent years, there is continued commercial interest in the cultivation of mushrooms with medical and pharmacological value. In Brazil, research and development of cultivation techniques, selection of strains to increase mushroom yield and production of bioactive molecules is needed as the industry is relatively young (1990’s) and is focused on the mushroom formerly known as Agaricus blazei or A. brasiliensis. Recent studies have clarified the taxonomic status of these fungi and they are considered to be synonyms of A. subrufescens however the name A. brasiliensis is used in many publications on the Brazilian medicinal mushroom. In this paper we evaluate medicinal strains presently cultivated in Brazil, strain ATCC 76739 and wild strains of A. subrufescens from various countries for i) mycelial growth at different temperatures, ii) mycelium efficiency to colonize the substrate, and iii) mushroom yield under various cultivation conditions (spawn rate, light, cold shock). Most of the medicinal cultivars showed higher mycelial growth rates than the wild A. subrufescens. A temperature of 35°C was not lethal for the cultivars, but seemed so for two A. subrufescens strains. Cultivation experiments were performed using commercial compost used for A. bisporus. The efficiency of compost colonization was estimated by measuring H2O2 after 20 days of incubation. Cultivars produced variable concentrations of H2O2 (39-217 nmoles/g of compost) whilst low concentrations were found in the group of wild A. subrufescens (47-91 nmoles/g). There was no relationship between compost colonization and others parameters studied (yield, time to fruiting and sporophore mean weight). When taken as a whole, the group of cultivars differed from the group of wild strains for the time taken to first fruiting, yield and sporophore mean weight. Cap colour also separated the cultivars from the wild strains. ATCC 76739 grouped with the cultivars for the various traits analysed. Light and cold shock had no significant effect on the time to first fruiting and yield. Valuable wild material useful for productivity and breeding was identified.