VIEW ARTICLE

Resistance

Interactions Between Virulent Isolates of Cronartium quercuum f. sp. fusiforme and Loblolly Pine Families of Varying Resistance. H. R. Powers, Jr.,, Chief research plant pathologist, U. S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Carlton Street, Athens, GA 30602; F. R. Matthews, principal research plant pathologist, U. S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Carlton Street, Athens, GA 30602. Phytopathology 69:720-722. Accepted for publication 29 January 1979. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-720.

Nine half-sib families of loblolly pine seedlings with varying degrees of resistance were artificially inoculated with five highly virulent isolates of Cronartium quercuum f. sp. fusiforme from diverse geographic areas. Significant differences were found in resistance among the host families. There also were significant differences in infection levels produced by the various rust isolates. All five pine families previously rated as resistant had relatively low levels of infection, but only one was resistant to all five rust isolates. The two families intermediate in resistance showed adequate resistance to at least one of the rust isolates. These interactions between pine families and rust isolates were statistically significant. The different genetic bases of resistance displayed by these host lines could be utilized in the development of rust-resistant pine seed orchards in specific geographic areas.