Chestnut blight (Cryphonectria parasitica) is successfully controlled with the hypovirus CHV1. By using molecular markers, the dissemination of nuclear (n) DNA and mitochondrial (mt) DNA of the hypovirulent strain can be followed in vitro and in vivo. In vitro pairings of a virulent and a hypovirulent strain of the same vc type resulted in 100% transmission of the hypovirus. Depending on the C. parasitica acceptor isolate, mtDNA was either not transferred at all or transferred at a rate of 80% to 100%. Mitochondrial hybrids were never found, mtDNA transfer was independent of the presence of CHV1. Whereas the transmission of CHV1 was bi-directional in strains of the same vc type, the transmission of mtDNA was uni-directional. The mitochondrial haplotype "a*" was easily replaced by other mitochondrial haplotypes.
Transfer of mtDNA was also demonstrated in Castanea sativa plants that were simultaneously inoculated with CHV1-free and CHV1-infected C. parasitica strains. 80% of the CHV1-infected re-isolates with the nuclear pattern of the acceptor strain showed the mtDNA pattern of the donor strain.