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Resistance

The Potential for Increased Virulence of Cronartium fusiforme on Resistant Loblolly Pine. H. R. Powers, Jr., Chief Plant Pathologist, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Carlton Street, Athens, Georgia 30602; F. R. Matthews(2), and L. D. Dwinell(3). (2)(3)Principal Plant Pathologists, U.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Carlton Street, Athens, Georgia 30602. Phytopathology 68:808-810. Accepted for publication 4 November 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-808.

Aeciospores of C. fusiforme were collected from individual rust galls on progeny of a resistant loblolly pine parent tree and from galls representing the general rust population on nearby trees. Seedlings of three half-sib families then were inoculated with basidiospores derived from each of these individual galls. These families included seedlings of the resistant source from which half of the aeciospores were collected, a second resistant family, and a susceptible check. The percentages of infection on both resistant families were significantly less than on the susceptible check family. There were no statistically significant differences in virulence between the inocula collected on resistant seedlings and the wild-type inocula. However, there was a slightly higher level of virulence among the inocula originating from the resistant family.

Additional keywords: disease resistance, fusiform rust, epidemiology, Pinus taeda.