Heat resistance, biology and prevention of Diehliomyces microsporus in crops of Agaricus species

Abstract

Soon after its introduction the mushroom species Agaricus bitorquis, which is immune to virus disease and prefers a warm climate, was threatened by the competitor Diehliomyces microsporus, false truffle. This fungus also likes warmth, and used to occur in crops ofA. bisporus.Mycelium and ascocarps were grown on several nutrient media. Optimum temperatures for mycelial growth were 26~ and 32~ with a slight depression at 30~ In trials in isolated growingrooms strain Somycel 2.017 of A. bitorquis was generally used since it appeared to be highly sensitive to the competition of false truffle. Inoculation with mycelium, ascocarps or ascospores of D. microsporus nearly always resulted in the presence of the competitor and in decreased mushroom yields. Even ten spores per m 2 caused D. microsporus. The time of inoculation was most important: irrespective of the kind of inoculum, inoculation only resulted in both false truffle and yield loss, if applied from spawning until a few days after casing. Inoculation at a later date could result in false truffle, but yield was not decreased.As germination in vitro of ascospores failed, even after addition of various triggers, ascospore suspensions were treated at various temperatures for several periods, Then mushroom growing trays spawned with Somycel 2.017 were inoculated with the treated suspensions giving 7 11 x 10 v spores/m z. The ascospores could not withstand 85~ for 0,5 h, 80~ for l h and 70~ for 3 h. Spontaneous incidence of false truffle, however, could not always be prevented and interfered with the results of these trials. It is possible that the thermal death-point of the ascospores is below 85 ~ Fruiting bodies and ascospores did not survive 'peak-heating' at the beginning and cooking out (compost temperature 12 h at 70~ at the end of a crop. After cooking out, however, D. microsporus could still be present in the wood of trays and contaminat~ a following crop if no wood preservative was applied.Yield of Somycel 2.017 was reduced by the competition of D. microsporus much more than yields of other strains of A. bitorquis. The least sensitive were the highly productive strains Horst K26 and Horst K32.The effects of fungicides on D. microsporus in vitro and in growing trials did not correspond. The fungicides tested so far could not prevent or control D. microsporus. Growing of less sensitive strains of A. bitorquis together with sanitary measures early in the crop and at the end of the crop, however, can prevent the competitor.

Contribution to the taxonomy and pathogenicity of fungicolous Verticillium species. II. Pathogenicity

“…Mushrooms of A. bisporus and A. bitorquis were grown as described by Bollen and Van Zaayen (1975), and Van Zaayen and Van der Pol-Luiten (1977), respectively. The growing temperatures were 25 ~ during mycelial growth and 16 -18 ~ during harvesting for A. bisporus, and 30 ~ during mycelial growth and 25 ~ during harvesting for A. bitorquis.…”

Isolation and mycelial growth of Diehliomyces microsporus: effect of culture medium and incubation temperature

“…In all the media, the null diameter at 15 o C increased gradually according to a temperature increase from 20 to 25 o C. It reached its maximum peak at around 30 o C, after which it decreased quickly when incubated at 35 o C, when the colony diameter was null again. Different results were presented by Zaayen and Pol-Luiten (1977) Tukey's test: means followed by different letters in the column are significantly different at 5%. CSDA: compost-soil-dextrose-agar; PCDA: potato-compost-dextrose-agar; OCDA: oat-compost-dextrose-agar; CDA: compostdextrose-agar; PDA: potato-dextrose-agar; ODA: oat-dextrose-agar.…”

“…From its first isolation, accomplished by Diehl and Lambert (1930), it was deduced that oats medium and soil extract favored the mycelial growth. Pol-Luiten (1977 and1978) obtained the best mycelial growth in malt and potato medium; however, this growth demonstrated an instability in the formation of the colony. There have been several studies in relation to incubation temperature.…”

Disease resistance in protected crops and mushrooms

“…van Zaayen & van der Pol-Linton (1977) examined various strains of A . van Zaayen & van der Pol-Linton (1977) examined various strains of A .…”