Somatic Incompatibility in Heterobasidion annosum and Phellinus weirii : Root and Butt Rots

Uppsala

International Union of Forest Research Organizations, Swedish University of Agricultural Sciences

1994

S. 323-333

21 Lit. Ang.

Bandaufführung

73675

Somatic compatibility (SI) was studied in vitro by pairing heterokaryons of defined composition and observing the nature of the interaction and the frequency of compatible interactions. In Heterobasidion annosum, a gap between the interacting colonies signified an incompatible reaction; in Phellinus weirii, incompatible interactions were marked by a pigmented line of demarcation. About 12% of the pairings between heterokaryons differing at only one, sib-related, nucleus were compatible in Heterobasidion annosum. In Phellinus weirii the proportion was 50%. This is consistent with control of SI by genes at 3 and 1 loci, respectively. Both fungi exhibited homogenic somatic compatibility, with multiple alleles at at least one locus. The mating type locus does not control SI in either fungus. Vegetative mycelia of Heterobasidion annosum were composed of mixtures of homokaryotic and heterokaryotic hyphae. In incompatible SI reactions, homokaryotic hyphae met and fused in the gap between the incompatible heterokaryons. The resultant "gap" heterokaryons were often a recombined genotype, containing nuclei from both parents. This novel form of genetic reassortment may be important in maintaining pathogen fitness during the colonization of stumps and wounds.