Genetic architecture underlying response to the fungal pathogen Dothistroma septosporum in lodgepole pine, jack pine, and their hybrids

In recent decades, Dothistroma needle blight (DNB), a pine tree disease
caused by the fungal pathogen Dothistroma septosporum, has severely
damaged lodgepole pine (Pinus contorta Dougl. ex. Loud.) in British
Columbia, Canada, and raised health concerns for jack pine (Pinus
banksiana Lamb.). The pathogen has already shown signs of host shift
eastward to the hybrid populations between lodgepole pine and jack pine
(Pinus contorta ´ P. banksiana), and possibly into pure jack pine.
However, we have little knowledge about mechanisms of resistance to D.
septosporum, especially the underlying genetic basis of variation in
pines. In this study, we conducted controlled inoculations to induce
infection by D. septosporum and performed a genome-wide case-control
association study with pooled sequencing (pool-seq) data to dissect the
genetic architecture underlying response in lodgepole pine, jack pine, and
their hybrids. We identified candidate genes associated with D.
septosporum response in lodgepole pine and in hybrid samples. We also
assessed genetic structure in hybrid populations and inferred how
introgression may affect the distribution of genetic variation involved in
D. septosporum response in the studied samples. These results can be used
to develop genomic tools to evaluate DNB risk, guide forest management
strategies, and potentially select for resistant genotypes.