Sexual and Other Relationships in the Genus Agaricus

Abstract

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 ...

Breeding relationships among several species of Agaricus

“…Our mating-type design;~tions in A . birorqrris do not correspond to those assigned by Raper and Kaye (1978).…”

“…Because clamp connections are absent, the criterion used to assay compatibility or incompatibility in pairings of homokaryons is formation of a genetically stable heterokaryon and (or) fruiting competence. Other studies (Raper 1976;Raper and Kaye 1978;Elliot 1978) have shown that A. bitorquis (Quel.) Sacc., a wild relative of A. brvrznescens, is unifactorially heterothallic and that most basidia produce four homokaryotic, self-sterile spores.…”

Maintaining Two Mating Types: Structure of the Mating Type Locus and Its Role in Heterokaryosis inPodospora anserina

“…Like in the case of P. anserina, it is not clear how heterokaryosis could be maintained in this fungus (Raper et al 1972;Raper and Kaye 1978). A first candidate is anastomosis.…”

Sexuality and Genetic Identity in the Agaricus Section Arvenses

“…Single-spore isolates from a collection identified as A. arvensis produced mating reactions among single-spore progeny, but were later shown to interact with several other Agaricus collections, including A. bitorquis (1,43). The tentative nomenclature of such collections in previously published work, which does not include detailed taxonomic data, should therefore be regarded with caution.…”

“…In some cases, authors have described heterothallic behavior with matings between single-spore isolates (17,18,43,50) and fruiting of heterokaryons in compost culture (19,50). With other collections, successful pairings could not be established (1,17,43), and occasional fruiting of single-spore isolates was described (17,50). It was hypothesized that the partial fruiting response of single-spore progeny could represent homokaryotic fruiting of a heterothallic species (17).…”