Thirty-three collections of Agaricus from nature and several strains of cultivated Agaricus bisporus were compared by 16 criteria including type of sexuality, interfertility patterns, macroscopic and microscopic morphology, growth and cultural characteristics, production of extracellular enzymes, and isoenzyme patterns for one enzyme. All but three of the collections fell into six distinct groups as defined with respect to all criteria examined. Members within each group are clearly related, but relationships between groups could not be established. Sexuality and interfertility patterns are important criteria for distinguishing relatedness among the collections. The correlations observed provide a new and useful base of reference for the classification of members of the genus Agaricus. Several aspects of the basic biology of the genus have also been revealed.
I N T R O D U C T I O NIt is particularly difficult to distinguish between members of the genus Agaricus by the classical method of comparing fruit-body characteristics. The difficulty lies in the continuous range of fruit-body types within the genus and the wide degree of variability within species. A knowledge of the basic biology of representative species would contribute to an understanding of their inter-relatedness. Such knowledge, helpful in the delineation of species, is available for only two : the famous, fully domesticated Agaricus bisporus (Lange) Imbach (Miller, 1971; Elliott, 1972;Raper, Raper & Miller, 1972;Miller & Kananen, 1972), and the wild, but cultivatable Agaricus bitorquis (Quelet) Saccardo (Raper, 1976a, b;Fritsche, 1976). The biology of the many other forms found in nature has remained obscure.The purpose of this work was to clarify the relationships between members of the genus Agaricus by a comparative analysis of their biological characteristics. Type of sexuality, interfertility, nuclear number in cells, enzyme production and general growth characteristics were determined and compared for several progeny from each of 33 specimens collected from nature and for several strains of cultivated A . bisporus. The characteristics examined, other than fruit-body morphology, were chosen either for their relevance to breeding or for their capability of distinguishing between stocks while remaining constant among progeny within stocks. The base of reference throughout the study was the biology of the two well-defined species, A . bisporus and A . bitorquis. The analysis has permitted a new definition of groups within the genus.
METHODS
Stocks.Specimens from nature were requested from many collectors in the U.S.A. and elsewhere. A total of 38 were received, each in the form of a spore print usually accompanied by the fruit body; each specimen was identified by the collector or a collaborator. Attempts were then made to germinate the spores, and the fruit bodies were preserved by slow drying. The analysis proceeded with only those 33 specimens from which we were able to germinate spores and obtain viable progeny (Table 1). In addition, seven ...
