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The Effects of Growth Regulating Compounds on Healthy and Blister Rust-Infected Tissue Cultures of Pinus monticola. A. E. Harvey, Plant Pathologist, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401; J. L. Grasham(2), and C. C. Waldron(3). (2)(3)Biological Technician, and Biological Aide, respectively, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401, stationed in Moscow, Idaho 83843, at Forestry Sciences Laboratory, maintained in cooperation with the University of Idaho. Phytopathology 61:507-509. Accepted for publication 18 November 1970. DOI: 10.1094/Phyto-61-507.

With increasing concentration, indoleacetic acid (IAA) (0.1-10.0 mg/liter), napthaleneacetic acid (NAA) (0.01-1.0 mg/liter), or 2,4-dichlorophenoxy-acetic acid (2,4-D) (0.01-10.0 mg/liter) progressively enhanced growth of both Pinus monticola and Cronartium ribicola in tissue culture. At concentrations above 3 mg/liter, 2,4-D inhibited fungus growth. Kinetin, in combination with these auxins (1/1 to 1/10 ratio), did not affect growth but did increase vigor and longevity of both organisms. The high auxin levels (above), particularly in combination with kinetin, induced formation of aecialike bodies by the pathogen. Gibberellic acid (0.01-1.0 mg/liter) had no observable effect on host tissues, but inhibited both the growth of the fungus and its formation of aecialike bodies. High concentration of kinetin (1.0-5.0 mg/liter), in combination with high sugar levels (2-5%) in tissue culture media, stimulated formation of a red pigment in the surface layers of host tissues, and subsequently caused reduction in the growth of both host and fungus.

Additional keywords: gibberellin, host-parasite interactions.