Studies on the morphogenesis of Agaricus bisporus: the dilemma of normal versus abnormal fruit body development

Development of mushrooms is driven by genetic and epigenetic factors in a c ontinuous interaction with the environment. It is assumed that each success ive stage of morphogenesis depends on specific sets of signals arising at t he appropriate time and place during the growth process. Morphogenetic dyna mism proceeds in a time dimension through a cascade of signal-effect associ ations. Developmental errors may occur when such signals originate in the w rong place and/or at the wrong time. As a result various abnormalities such as ectopic tissues can develop and morphogenesis can be severely disturbed . Both endogenous genetic disturbances and exogenous factors can cause deve lopmental errors. Lamellar dysplasia, which is a pore-like proliferation of the gills, forms an example; it may be induced experimentally. Both lamell ar dysplasia and rosecomb disease of Agaricus bisporus result from endogeno us genetic instability, whereas the developmental errors observed in wet bu bble disease, which is caused by the infection of Mycogone perniciosa, orig inate from an exogenous factor. Morphogenesis normally leads to a symmetric al form of primordia of A. bisporus. Asymmetry is very frequently associate d with an underlying pathological situation. Defining exact criteria of and sharp borderlines between normal and abnormal development seems infeasible . Fungi may readily tolerate morphogenetic imprecision. In this report, var ious macro- and microscopic features of normal and pathological development are illustrated; the dilemma of normal versus abnormal fruit body developm ent has been discussed.