White pine blister rust resistance in North American, Asian and European species - results from artificial inoculation trials in Oregon

Dorena Genetic Resource Center (DGRC) has used artificial inoculationtrials to evaluate progenies of thousands of Pinus monticola and P. lambertiana selections from Oregon and Washington for resistance to white pine blister rust caused by Cronartium ribicola. In addition, early results are now available for P.albicaulis and P. strobiformis. DGRC has also recently evaluated seed orchard progenies of P.strobus, as well as bulked seedlots from P. armandii and P. peuce.The majority of P. monticola, P. lambertiana, P. albicaulis, and P. strobus progenies are very susceptible to blister rust. However, resistance exists in all these species. P.strobiformis showed relatively high levels of resistance for the eight progenies tested.Resistance in P. armandii was mainly reflected in the very low percentage of cankered seedlings; for P. peuce, the high percentage of cankered seedlings alive three years after inoculation was notable. R-genes are present in some of the North American five-needle pine species, but partial resistance traits (e.g. bark reaction)will play a major role in breeding activities for P. monticola and P. lambertiana and will likely be the key to developing durable resistance.