Didymium ovoideum culture and mating system

Abstract

Reliable spore to spore culture of Didymium ovoideum was achieved using a high CaCl₂ fruiting medium. Fourteen isolates from southwestern Virginia 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 was highly skewed with one of the mating types (usually A²) missing or greatly 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 distinct biological species.

Key Words:

• Didymium ovoideum
• heterothallism
• mating types