Virulence and Interfertility ofChondrostereum purpureumIsolates

Five families of single-spore isolates of the bioherbicide fungusChondrostereum purpureumexhibited tetrapolar mating patterns when paired in culture. Compatible cultures formed detectable hyphal clamp connections in agar cultures only after subculturing on fresh media. Pairings of allopatric isolates resulted in compatible interactions, indicating unrestricted outcrossing ability. Inoculations of tissue cultures of thimbleberry (Rubus parviflorus) indicated a range of virulence among single-spore isolates (monokaryons) and dikaryons, but dikaryons had no greater virulence than their component monokaryons. Likewise, hybrid dikaryons of single-spore isolates showed no greater virulence than their single-spore components on inoculated poplar (Populus balsamiferassp.trichocarpa) stem cuttings.