Are terpenes involved in cross induction of systemic susceptibility between Heterobasidion annosum and Diplodia pinea in Italian stone pine?.

The recent finding of the North American P (Nam-P) type of Heterobasidion annosum in Italian pinewoods opens up some intriguing questions about its behaviour on the hosts and also on the possible interactions with local fungal pathogens. This study showed that infection of Italian stone pine (Pinus pinea) with H. annosum, both European P (Eur-P) and Nam-P isolates, increases susceptibility of pine to Diplodia pinea shoot blight. This systemic increase in susceptibility was associated with systemic alteration of terpene metabolism. The study showed that pines inoculated with the Nam-P isolate became more susceptible to D. pinea than hosts inoculated with the Eur-P isolate. The significance of these results will be discussed in the context of current models of conifer defense against pathogens as well as the effects of exotic pathogens on native ecosystems.