Incompatibility reactions and nuclear condition of three Phellinus species

Graduation date: 1982Phellinus arctostaphyli (Long) Niemela, P. igniarius\ud (L. ex Fr.) Quel., and P. tremulae (Bond.) Bond. et Boriss.,\ud heartrotting hymenomycetes in the family Hymenochaetaceae\ud (Aphyllophorales), all conform to a multi-allelic heterothallic\ud mating system. Both compatible and incompatible\ud reactions result from pairings of homokaryons from the same\ud basidiocarp. Homokaryons isolated from different basidiocarps,\ud but the same species, are fully compatible. Cultural\ud characteristics are not useful in distinguishing between\ud homokaryons and heterokaryons. However, heterokaryons\ud exhibit significantly faster growth rate in culture than\ud homokaryons. Antagonistic responses between paired homokaryotic\ud isolates serve as an indicator of sexual incompatibility;\ud sexually compatible pairs acquire the faster growth\ud rate of heterokaryons. Antagonistic characteristics similar\ud in appearance to sexual incompatibility occur between paired\ud heterokaryotic isolates displaying vegetative incompatibility.\ud These three species are similar in the variation of the\ud nuclear condition throughout their life cycles. Basidiospores are produced with one nucleus, but are ordinarily binucleate\ud prior to germination. Both homokaryons and heterokaryons\ud have a variable number of unpaired nuclei between septa.\ud The dikaryophase is delayed until basidiocarp formation,\ud when the dikaryon can be found in young basidia and mycelium\ud underlying basidia. Incompatible reactions in hybridization\ud attempts support the segregation of these three closely\ud related species