Strain improvement in the cultivated mushroom Agaricus bisporus

Summary Early attempts at genetic improvement in the cultivated mushroom Agaricus bisporus (Lange) Imbach were empirical, for little was understood of its natural breeding system. The mushroom is now known to be a secondarily homothallic species with a single multiallelic mating-type factor. This better understanding makes it possible to evaluate those breeding methods previously used and to suggest alternatives.Strain selection alone based on single spores, multispores or tissue culture may give improvement in the short term but it is unlikely to be as effective as methods involving controlled crossing. Mixing fertile strains may produce hybrids but it is difficult to identify them. It is better to use non-fertile isolates because only hybrids fruit. The earlier recognition of hybrids can be achieved using markers which are expressed in culture and genetic resistances may be especially useful in this respect.There is also a possible role for other Agaricus species which may be grown commercially and are more amenable to genetic manipulation than is A. bisporus.