Volume 10 Part 2 Article 26: Heat Resistance, Some Biological Aspects and Prevention of False Truffle (Diehliomyces microsporus)

Volume 10 Part 2 Article 26
Year 1979
Title: Heat Resistance, Some Biological Aspects and Prevention of False Truffle (Diehliomyces microsporus)
Authors: A.M. van Zaayen and B. Van Der Pol-Luiten

Abstract:

Soon after the first crop, in 1974, of a commercial variety of Agaricus bitorquis (Quel.) Sacc. that is immune to mushroom virus disease (van Zaayen, 1976), a competitor even more dreaded than this disease reappeared. Diehliomyces microsporus (Diehl and Lambert) Gilkey, “false truffle”, was first observed in crops of the cultivated mushroom Agaricus bisporus (J. Lange) Imbach in Ohio in 1929 (Lambert, 1930) and described by Diehl and Lambert (1930) as Pseudobalsamia microspore. Gilkey (1954) reclassified the fungus from the Tuberales into the Eurotiales and named the genus Diehliomyces. Spores of D. microsporus were reported to withstand at least 82°C for 5h (Lambert, 1932). Beach(1937) mentioned an optimum temperature for mycelial growth of 28°C, which covered the frequent association of false truffle with warm weather.

Over the years, the fungus caused a substantial annual loss in crops of A. bisporus in the United States and Great Britain (Kligman, 1944). In recent years false truffle was hardly noticed in crops of A. bisporus, most probably because environmental conditions were better controlled, e.g., temperature in the growing-rooms. During the hot summers of 1974 and 1975, the fungus was observed in crops of A. bisporus, but yield was only slightly reduced (Olivier and Guillaumes, 1975). However, A. bitorquis requires higher growing temperatures than A. bisporus: 30°C during mycelial growth in the compost and 25°C during cropping (Hasselbach and Mutsers, 1971; Pompen, 1975). These conditions appeared to be most favourable to false truffle. From 1974, crop yield of A. bitorquis, commercial variety “Somycel 2.017”, was considerably reduced. The present study deals with properties of D. microsporus in vitro and in vivo and trials to control or prevent this fungus.

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