DIDYMIUM-OVOIDEUM CULTURE AND MATING SYSTEM

Reliable spore to spore culture of Didymium ovoideum was achieved usin g a high CaCl2 fruiting medium. Fourteen isolates from southwestern Vi rginia and northern West Virginia were investigated and all displayed a heterothallic mating system. Only two mating types (A1 and A2) were uncovered, and in all 14 isolates the mating type segregation ratio wa s highly skewed with one of the mating types (usually A2) missing or g reatly reduced in frequency. No plasmodia were produced when clones of these mating types were crossed to all known Didymium iridis sibling species mating type testers. This suggests that D. ovoideum is a disti nct biological species.