Volume 10 Part 1 Article 52: Fructification of Agaricus bisporus (Lge.) IMB. in Relation to the Relevant Microflora in the Casing Soil

Volume 10 Part 1 Article 52
Year 1979
Title: Fructification of Agaricus bisporus (Lge.) IMB. in Relation to the Relevant Microflora in the Casing Soil
Author: H.R. Visscher


Since 1960, when Eger introduced the “Halbschalen” test, it has been believed that bacteria in the casing soil – identified in English soil as Pseudomonas, Group IV or ft. putida (Hayes et al., 1969; des Thomas et al. 1964) are indispensable for fructification in A. bisporus.

Eger’s idea’s and Tschierpe’s opinion (Tschierpe, 1959; Tschierpe and Sinden, 1964, 1965), that a fall in concentration of CO2 would be sufficient for onset of fructification, were reconciled by Long and Jacobs (1968), who showed that under non-sterile conditions the best fructification occurred with a volume fraction of CO2 in the range 0.3-1 dm3/m3 (=0.03-0.1%). Under sterile conditions, no fructification started, whatever the concentration of CO2.

Eger’s reasoning (1961) that the bacteria would thrive on volatile metabolites from the mushroom mycelium (Lockard and Kneebone, 1962) was confirmed by Hayes et al. (1969) and Eger (1972), culturing the bacteria on one or more of those metabolites as sole carbon source.

Since some fructification occurred under sterile conditions in the presence of activated charcoal (Eger, 1961; Long and Jacobs, 1974; Angeli-Couvy 1975, 1977), Long and Jacobs concluded that the absorbent action of the charcoal would serve as a model for the microbial effect in inducing mushroom formation. More authors liked to reduce the role of the relevant microflora to a mere removal of excess volatiles or self-inhibitors of fruiting (Stoller, 1954; Wood, 1976). Their opinion will be discussed in this paper. The ideas on the relevant microflora described so far originated from trials on a laboratory scale. In this paper, I will give an impression of ways of checking or extending those ideas on a more practical scale, mainly in the growing rooms of our Mushroom Experimental Station, whose facilities have been described earlier (Pompen and Gerrits, 1972).

The trials were carried out either in experimental plots in shelves of 1.3 m2 in growing houses of 120 m2 or in trays of 0.27 m2 in growing houses of 25 m2 both treated as a one-zone system. In the houses, there were 5 layers with 16 plots or 18 trays in one layer. In most of the trials factorial designs were used such as a 24 or 4 x 2 x 2 or 2 x 3 x 3 layout with 4 or 5 replicates. The layers were considered as blocks and the treatments were randomized in the layers.

Our main line of research may be expressed perhaps best as to look for and to understand those cultural practices and treatments that provide the best ecological conditions in the casing soil to harbour the relevant microflora and so to obtain, what has been called by Flegg (1956) the main function of the casing layer : “production of mushrooms in quantity”.

To illustrate this line of research I will describe an assortment of trials, some reported earlier (Visscher, 1973, 1975a, b ; Van Gils and Visscher, 1975), each giving some pieces of information.

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