Volume 10 Part 1 Article 25: Some Differences in Response to Competitive Microorganisms Deciding on Growing Success and Yield of Wooddestroying Edible Fungi

Volume 10 Part 1 Article 25
Year 1979
Title: Some Differences in Response to Competitive Microorganisms Deciding on Growing Success and Yield of Wooddestroying Edible Fungi
Author: G. Gramss

Abstract:

The knowledge on cultural pretensions of higher fungi reached in certain fields a remarkable degree, but little contributes to the problems of mushroom growing. This disproportion between impressive advances in theory and the lack of technologies for obtaining fruit bodies is particularly pronounced in case of ectomycorrhizal fungi.

Attempts made in cultivating soil-inhabiting mushrooms led to better results. Extensive studies had been undertaken by Hlavacek (1952) on Agaricus sp., Poppe (1971/72) also on Agaricus sp., Manz (1971) on Lepiota, and Gramss (1976) on Agaricus, Macrolepiota, Lepista, Clitocybe, Morchella, Calocybe, and Lyophyllum. The author offered Agaricus macrocarpus to be the only species found among 50 wild isolates which was qualified for being grown commercially. The substrate composition for soil-inhabiting mushrooms seems to be of second-rate importance, while some problems of viability dominate. It is surprising to observe that nearly 50% of freshly isolated strains from soil-inhabiting mushrooms cannot develop in nonsterile substrates. This feature complicates the growing technique of Agaricus macrosporus (Uzonyi, 1967), and Agaricus arvensis (Zadrazil et al., 1973), and prevents each progress in growing Agaricus campestris and A. fissuratus being two species which appear nearly epidemically on manured grassland. The sterile spawn of both species frequently dies back even under the attack of airborne infections after having opened the sterile spawn container. The results obtained with artifical inoculations of meadows and forest stands including Agaricus, Macrolepiota, and Lepista sp. (Gramss, 1977a) make us suppose that viability and virulence of the mushroom mycelium is promoted indirectly by certain green plants and their rhizosphere microflora. Similar results are reported by Garrett (1960). In soil inoculations using antibiotic releasing saprophytic fungi for controlling plant root diseases, the introduced fungus failed to produce antibiotics. Garrett concluded that antibiotic production is limited to the immediate substrate or “ecological niche” of the saprophyte.

Little is known about the nature of an “ecological” environment allowing maintenance of an artifical inoculum. Rawald (1962) determined vitamine traces to be an ecological factor in Tricholoma. Fries (1949) emphasized both vitamines and amino acids to be of ecological worth in case of the genus Mycena. But despite feeding optimum substrates which contain these ingredients, the virulence of certain soil-associated mushrooms is not to be improved, and there is some evidence to believe that virulence is mainly represented by the antibiotic activity of the mushroom. Release of antibiotics should enable the mushroom mycelium to suppress antagonistic microorganisms which block the uptake of soil nutrients.

It is shown by Moser (1959), Haselwandter (1973), and others, that ectomycorrhizal fungi synthesize indole substances which first allow to form the mycorrhizal symbiosis. These indoles are produced from tryptophane growing the mycorrhizal fungus in monoxenic culture, or from anthranilic acid growing the mycorrhizal fungus in polyxenic culture in combination with bacteria accompanying the mycorhizosphere. In the latter case, each microorganism alone was unable to synthesize indoles from anthranilic acid. As to saprophytic soil mushrooms, there is no evidence that chemical precursors produced by certain microorganisms facilitate synthesis of antibiotics by the .mushroom, but interrelations like those have to be hypothesized. The presence of these microorganisms would be the most essential characteristic of an “ecological niche”.

While composts for growing soil-inhabiting mushrooms differ greatly in composition of nutrients, progress of pre-degradation, and presence of more or less inhibitory competitor microorganisms, both wood and straw are substrates which are fairly homogeneous in chemical constitution. Moreover, compact wood pieces with their internal sterility should allow fungal development uninfluenced by competitor microorganisms. Really, most of the mushroom species being grown industrially are wood inhabitants. In the present study, the competitive force of wood- and straw-degrading mushrooms is estimated as far as facilitating an artifical culture.

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