Volume 10 Part 1 Article 6: Comparative Cytology in the Genus Agaricus

Volume 10 Part 1 Article 6
Year 1979
Title: Comparative Cytology in the Genus Agaricus
Authors: Hsing-Hsiung Hou and T. Elliott


In the life-cycle of the typical heterothallic basidiomycete there are two contrasting mycelial phases. A single spore germinates to produce a mycelium in which the individual cells are uninucleate and the nuclei are all of the same genotype. This mycelium is termed primary or monokaryotic and does not normally fruit. Compatible monokaryons combine to form a secondary mycelium or dikaryon. In the dikaryon the cells are regularly binucleate, the members of each pair being of contrasting parental genotypes. This type of nuclear cycle, exemplified by fungi such as Schizophyllum commune, has been classified as “normal” (Boidin, 1971; Kuhner, 1977) and seems to predominate in the homobasidiomycetes.

Four Agaricus species have so far been shown to be heterothallic ; A. bisporus (Miller, 1971; Raper C.A. et al., 1972; Elliott, 1972) A. bitorquis (Raper C.A., 1976; Elliott, 1978) A. macrosporus and A. nivescens (Elliott, 1978, and this Symposium). In A. bisporus mycelia capable of fruiting (heterokaryons) and those derived from aberrant 4-spored basidia which are not fertile (homokaryons) are both multinucleate, (Evans, 1959; Elliott, 1971). By contrast C.A. Raper (1976) has shown in A. bitorquis that whereas the mycelia derived from singlespores are multinucleate the mycelia of fruiting i-solates tend to be regularly dikaryotic.

Nuclear distributions in homokaryons and heterokaryons of A. macrosporus and A. nivescens, two species which have not previously been studied, are described here and compared with those in A. bisporus and A. bitorquis.

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