| Summary: | Flammula alnicola (Fr.) Kummer, formerly called Flammula conissans Fr. sensu Ricken causes a yellow stringy butt rot of several conifers in Western Canada. It is usually of infrequent occurrence in conifers, but was found to be the most important butt rot of white spruce in the Smith - Slave Lake area of Alberta. An investigation was conducted to gain information on the biology of the fungus. The decay has a characteristic pattern caused through preference of the fungus for wood rays and early spring wood. A musty odor in decay and cultures is characteristic. The fungus invades white spruce through pressure wounds caused by root contacts but evidently does not invade recently formed wounds. The average linear rate of decay was one inch per year in two-year-old artificial infections but probably less in natural infections. The fungus decayed blocks of root and stem wood, and blocks of light and heavy density wood, slowly, but at similar rates. The occurrence of the decay was related to good sites, and non-calcareous soils with acid first mineral horizons. The mat of cultures is fine woolly, white becoming a pale yellow, growth slow. Microscopically cultures are characterized by the presence of clamp connections and allocysts. Optimum growth on malt agar occurred at 22° C. and at a pH of 4.4. Fruiting in culture was induced by aeration with nearly saturated air, a temperature of 54° F. and illumination of 8 to 30 foot candles. The fruit body of F. alnicola is a yellow mushroom which has a stipe with darker base, adnate lamellae, partial veil adhering to the edge of the pileus, hymenium without pleurocystidia; spores rusty brown, 4.5 - 5.5 x 7- 10 μovate ellipsoid, apiculate. Spores germinated on culture media only after cold treatment at -7° C. Cold treatment of spores at -18° C. inhibited germination. The fungus shows the tetrapolar type of interfertility. Parallel experiments with Flammula conissans (Fr.) Gillet were conducted to establish the two fungi as separate species. F. conissans has similar cultural characters except for a faster rate of growth and the absence of the musty odor characteristic of F. alnicola. Aeration inhibits initiation of fruiting in F. conissans. Fruit bodies are smaller, the base of the stipe is concolorous with the cap and pleurocystidia are present on the hymenium. Spores are rusty brown, 4 – 4.5 x 5.5 - 8 μ, oval oblong. F. conissans shows the tetrapolar type of fertility. Monosporous mycelia of F. alnicola and F. conissans are intersterile. F. alnicola because of its slow rate of growth and restriction to heartwood is relatively unimportant as a cause of wind throw in white spruce. Science, Faculty of Botany, Department of Graduate
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