Use of Taxon-Specific Competitive-Priming PCR to Study Host Specificity, Hybridization, and Intergroup Gene Flow in Intersterility Groups ofHeterobasidion annosum

IGarbelotto. M., Ratcliff, A., Bruns, T. D.. Cobb, E W.. and Otrosina, W. stumps or trees were S; isolates from pine stumps were 80% S and 20% J. 1996. Use of taxon-specific competitive-priming PCR to study host P; isolates from pine, incense cedar, and western juniper trees were 23% specificity, hybridization, and intergroup gene flow in intersterilit y groups S and 77% l? The recovery of a well-established hybrid “SP” genet in a of Phytopathology 86543-551. pine center was confirmed by isozyme analysis. The PCR amplification of the mitochondrial Mu-ML6 region also was diagnostic for the two ‘lXvo intersterility groups (IX&) of the forest pathogen Heterobasidion IS&, but in areas where both fir and pine mortality centers were present, annosum are found in California: S and I? We devised a polymerase chain about 7% of S isolates yielded the P-specific fragment. These results reaction (PCR) method called taxon-specific competitive-priming (TSCP) indicate the possibility of gene flow in nature between the two ISGs. The PCR to differentiate the two IS&. Using TSCP-PCR. we typed 537 live presence of S isolates on trees previously regarded as exclusive P hosts isolates and dry basidiocarps from 204 trees and 114 stumps from 60 broadens the potential host range of this ISG. sites in eight California national forests. All isolates from fir and sequoia The basidiomycete Heterobusidion annosum (Fr.) Bref. is regarded as a complex species containing at least three intersterility