Viral Transmission Between Heterobasidion parviporum Strains in Wood Billets and Decaying Stumps

The combined use of Heterobasidion partitiviruses HetPV13‐an1 and HetPV15‐pa1 is considered a promising biocontrol approach against Heterobasidion root and butt rot. Both viruses mediate debilitating effects in many Heterobasidion isolates and are transmitted efficiently in laboratory conditions. In this investigation, we conducted transmission experiments in a natural substrate (wood billets incubated outdoors) and the natural habitat (spruce stumps with pre‐existing H. parviporum infection) using H. parviporum isolates as donors and the indigenous strains as recipients. The overall transmission rates of HetPV13‐an1 and HetPV15‐pa1 were high in wood billets and slightly lower in naturally infected stumps, although still sufficient for biocontrol.