Intraspecies variation of mature Pinus taeda in response to root-infecting ophiostomatoid fungi

Seedling screening studies have shown intraspecies variation in susceptibility of Pinus taeda (loblolly pine) to Leptographium terebrantis and Grosmannia huntii, the causal agents of root infection in Pinus species. However, it is critical to understand the susceptibility of mature P.taeda trees. Roots of mature P.taeda families determined as susceptible and tolerant to L.terebrantis and G.huntii by previous seedling screening trials were artificially inoculated with the same fungal isolates. Dark necrotic lesion and vascular occlusion were recorded 8weeks later. Families previously considered as susceptible had relatively longer lesions and occlusions. The variation in susceptibility to the two fungi remained the same as exhibited by families in the seedling trial. These results suggest intraspecies variation in relative susceptibility of P.taeda to L.terebrantis and G.huntii remains similar regardless of the age of the tree.