ibclogo XVI International Botanical Congess


Abstract Number: 3159
Poster No. = 1782


THE MATING-TYPE SWITCH IN CRYPHONECTRIA PARASITICA


_R. E. Marra_ and M. G. Milgroom, Cornell University, Ithaca, NY.


Self-incompatibility in the ascomycete, C. parasitica, is controlled by a single locus (MAT), comprising two idiomorphs. Although only one or the other idiomorph occupies the MAT locus, self-fertile isolates also have the alternate idiomorph at very low titer. Some conidia (asexual spores functioning as male gametes) from self-fertile isolates have the alternate idiomorph at the MAT locus, suggesting that a mating-type switch replaces the resident idiomorph with a copy of the extrachromosomal alternate idiomorph. Because they are isogenic except at the MAT locus, switched conidia are sexually compatible with their parent thallus, supporting the hypothesis that switched conidia are required for self-fertilization. Our model for self-fertilization via this mating-type switch is supported by the observation that progeny of self-fertilization segregate 1:1 for MAT-1 and MAT-2.


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