Hybridization between species is being recognized as a major force in the rapid adaptive
evolution of fungal plant pathogens. The first stages of interspecific hybridization necessarily
involve nuclear-mitochondrial chimeras. In their 2001 publication, Olson and Stenlid
reported that mitochondria control the virulence of first generation hybrids between the North
American fungal pathogen Heterobasidion irregulare and its congeneric H. occidentale. By
assessing saprobic ability and gene expression of H. irregulare× H. annosum sensu stricto …