Genetic Resistance to Fusiform Rust in Southern Pines and White Pine Blister Rust in White Pines-A Contrasting Tale of Two Rust Pathosystems-Current Status and Future Prospects

Damage or mortality from pathogens can reduce productivity of forest plantations, as well as significantly harm natural forest ecosystems. Genetic resistance within the host species is the first line of defense for tree species. Resistance breeding programs for the native fusiform rust and exotic (to North America) white pine blister rust diseases are two of the longest concerted efforts in forest trees, spanning more than 50 years. Advances in developing greater genetic resistance have been made in both pathosystems, but unique challenges and opportunities in each system translate to different approaches. Fusiform rust resistance programs have mainly emphasized complete resistance, while partial resistance plays a prominent role in white pine blister rust resistance programs. Advances in the development of molecular genetic tools now permit investigations in conifers and their associated rust pathogens. Good progress has been made in identifying resistant populations and understanding resistance in these pathosystems, and resistant stock is now being used extensively for reforestation and restoration. These programs represent great success stories brought to fruition by the long-term efforts. However, continued support will be needed to enhance the level and fully realize the potential of durable genetic resistance in these invaluable North American conifer species.