Gremmeniella abietina types cannot be distinguished using ascospore morphology

Twenty-one Gremmeniella abietina var. abietina type A and 12 type B samples with ripened apothecia were collected in Sweden and Finland. Morphological dimensions of the ascospores were determined with an image analyser (Leica Qwin). Measured variables included length, width, perimeter and roundness of ascospores. Variations in these variables overlapped between the two types. Type A ascospores were significantly shorter (mean length 15.8 mu m) than the type B ascospores (mean length 17.1 mu m). Type A ascospores were also significantly rounder than type B ascospores. Differences between these morphological characters were, however, too small to distinguish the types as separate taxonomical species. Round-pointed and acute ascospores were found in the same apothecium but in different asci. According to the hypervariable marker GAAA1000, both round-pointed and acute ascospores originated from the same two parents in normal segregation.