Genetic Resistance in Douglas-fir to Damage by Snowshoe Hare and Black-tailed Deer

Abstract Genotype of Douglas-fir significantly affected feeding selection for foliage by both snowshoe hare and black-tailed deer in pen tests with captive animals. Nine clones were rated independently for each animal species. Genotypes preferred by deer and hare ranged up to 64 and 178 percent more attractive, respectively, than those least preferred. Order and magnitude of damage resistance in pen tests, as predicted for full-sib F1 progenies based on preference shown among clones, closely conformed to resistance traits indicated for parents. In one 4-family test, captive deer selected between resistant and susceptible families with feeding incidence levels of 41 and 78 percent, respectively, at the point of maximum difference between extremes. In another 4-family test, captive hare also showed comparable selection of 35 and 82 percent between extremes. Resistance to wild hare, in a 4-family field test with seedlings, also conformed closely to that predicted from preferences established in clonal pen tests. Damage incidence levels ranged from 56 to 86 percent for most resistant and susceptible families, respectively, after one winter's exposure to severe hare clipping. A later 4-family trial with seedlings exposed to wild hare in the field established close agreement among related materials in clonal pen tests, family pen tests, and family field tests. Differences were highly significant with the most resistant family damaged 37.5 percent and the most susceptible 62.5 percent after one winter. In this test, moreover, significant damage resistance was shown by 2 families during a second winter of exposure. Genetic analysis suggests that resistance to animals based on nonpreference is strongly inherited and chiefly additive. Forest Sci. 22:106-121.