The dissertation is devoted to the research of strains of mycophilic fungi of the genus Hypomyces (Fr.) Tul. & C.Tul. with Cladobotryum-like anamorph, which cause cobweb disease of Agaricus bisporus (J. E. Lange) Imbach on Ukrainian mushroom farms. The thesis covers different aspects of this problem: the species and strain diversity of Hypomyces spp. with Cladobotryum-like anamorph, isolated on Ukrainian mushroom farms, their cultural-morphological and micromorphological features, features of growth under different cultivation conditions. The paper presents experimentally obtained data on the fungicide resistance of Cladobotryum strains and antagonistic action of these strains against other species of fungi associated with the industrial production of mushrooms.
It was found that according to the symptoms of infection in A. bisporus caused by strains of Hypomyces spp. with Cladobotryum-like anamorph, we can distinguish two types of cobweb diseases: Type A and B.
A study of strains that cause cobweb disease type A found that they all belong to H. odoratus G. R. W. Arnold (anamorph: C. mycophilum (Oudem.) W. Gams & Hooz.) This species was first identified as a causative agent of cobweb disease on Ukrainian fungal farms. The study of strains that cause cobweb disease type B, showed their homogeneity in micromorphology and a significant difference from the most common species of the genus Cladobotryum. All strains that cause cobweb disease type B were conventionally designated as Cladobotryum sp. B. According to micromorphological and cultural-morphological features, these strains belong to the class that forms related species of C. tenue Helfer and C. rubrobrunnescens Helfer and require further study by molecular genetics methods.
It was found that H. rosellus (Alb. & Schwein.) Tul. & C. Tul. (anamorph: C. dendroides (Bull.) W. Gams & Hooz), which had been considered the main infectious agent that causes cobweb disease of A. bisporus, is not the main causative agent of this disease in Ukrainian fungal farms. Only 1 strain of C. dendroides was detected in our study.
It was found that according to the parameters of growth rate, the best medium for cultivation of all strains of of C. mycophilum is glucose-peptone-yeast agar medium (14-20 mm/day), slightly worse than malt extract agar medium (11-18 mm/day) and potato-dextrose agar medium (11-16 mm/day). The growth rate of strains from the Cladobotryum sp. group B on glucose-peptone-yeast agar medium was 13-15 mm/day, on potato-dextrose agar medium – 12-16 mm/day, on malt extract agar medium – 8.5-11.5 mm/day. The intensity and time of pigmentation development had strain differences and depended on the selected medium (MEA, PDA, GPDA), but in general the color intensity on the GPDA medium was higher than on MEA and PDA.
It was established experimentally that the optimal cultivation temperature of all Cladobotryum strains is a temperature of 25 oC and pH 6.9 is optimal for biomass accumulation for all strains of Cladobotryum isolated from fungal farms of Ukraine.
The fact of the spread of Hypomyces / Cladobotryum strains which was resistans to benzimidazole fungicides (benomyl, carbendazim) and prochloraz at the fungal farms of Ukraine was revealed.
It was shown that the strains of Hypomyces odoratus / Cladobotryum mycophilum and Cladobotryum sp. groups B are generally sensitive to fluazinam and metrophenone.It was found the ability of Hypomyces / Cladobotryum strains to inhibit the growth of other fungi , namely, Hypocrealixii / Trichoderma harzianum, Hypomyces perniciosus / Mycogone perniciosa, Aspergillus niger, Mucor sp., Penicillium sp.
The final result of the current research was a creation of a collection that contains 17 strains of Hypomyces (Fr.) Tul. & C.Tul. with Cladobotryum-like anamorph isolated from Ukrainian mushroom farms. For each strain, we made a detailed description, which includes data on species identification, growth characteristics, and morphology of colonies on different nutrient media, temperature regimes of cultivation and storage, critical temperatures, resistance to different types of fungicides, and antagonistic properties against others mycophilic fungi and fungi associated with compost and cover soil.
