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Mycelia of Gremmeniella abietina isolated from the same ascus were paired in seedlings of Pinus sylvestris and the production of apothecia determined. G. abietina was found to be a heterothallic fungus in which mating is controlled by a single locus composed of at least two mating allcles. Independent of climatic conditions isolates of type B produced greater number of apothecia than those of type A.
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Antti Uotila (1992) studied this question.
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