Ascospore Polymorphism in Gibberella Zeae

ABSTRACT

A range of ascospore morphologies was observed in several collections of perithecia of Gibberella zeae on Zea mays. In general, the basic ascospore condition appeared to be a spore with four, approximately equal-sized uninucleate cells. Three-celled ascospores sometimes occurred, one cell of which was binucleate and tended to be about twice the size of the others. In two-celled ascospores, both cells tended to be binucleate, while single-celled ascospores were binucleate. Ascospores of all four classes germinated on water agar with no changes in septation. Germination of three- and four-celled ascospores was almost exclusively from one or both end cells, while two-celled spores germinated from one or both cells. Taxonomic and evolutionary implications of these findings are discussed.

Key Words:

• Pyrenomycete evolution
• speciation
• alternative adaptations