The behavior of spores of M.perniciosa was examined in relation to infection of A.bisporus. Conidia in mushroom casing materials germinated in the presence of vegetative mycelium of A.bisporus, but germ tube growth was limited. Ghlamydospores occasionally germinated under these conditions, maximal germination occurring when in contact with mushroom initials. Germinating spores did not parasitise mycelium but infected mushroom sporophores at all stages of development. Washings and extracts of mushroom sporophores promoted germination of both spores, the stimulus being specific in the case of chlamydospores. In vitro studies indicated that glutamine and alanine promoted good germination of conidia but not to the levels obtained with mushroom extracts. Nutritional status of conidia was shown to vary with the growth media employed. Attempts to identify materials inducing chlamydospore germination were unsuccessful, but the methods of purification employed, suggested that an amino acid, peptide or related compound(s) might be involved. Infected mushrooms possess a higher dry/fresh weight ratio, have a higher respiratory rate, and expand more rapidly than healthy mushrooms. The appearance of rotting symptoms varied according to the time of infection of sporophores, but did not occur before the cellular-expansion phase of mushroom development. Following demonstrations of lytic enzyme production and mushroom cell wall degradation in vitro, the chemistry and ultrastructure of cell walls of parasite and host were examined to elucidate host-parasite relationships. Preliminary examination of lytic enzyme production in liquid culture by M.perniciosa is reported. Results obtained are discussed in relation to the mode of parasitism, and related to morphogenetic changes associated with the transition from vegetative to reproductive growth in A.bisporus. The chemical control of the disease using benomyl and thiabendazole was examined.
|Date of Award||1972|