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Leaf, Stem, Crown, and Root Galls Induced in Chrysanthemum by Agrobacterium tumefaciens. H. N. Miller, Plant Pathologist, Department of Plant Pathology, Institute for Food and Agricultural Science, University of Florida, Gainesville 32611; Phytopathology 65:805-811. Accepted for publication 18 February 1975. DOI: 10.1094/Phyto-65-805.

Leaf, stem, crown, and root galls induced by a chrysanthemum strain of Agrobacterium tumefaciens occur sporadically on chrysanthemum (Chrysanthemum morifolium). Bacterial isolates from leaf, stem, crown, and basal stem galls were morphologically and physiologically similar in comparative bacteriological tests for this organism, and gave identical pathogenic response when inoculated to many chrysanthemum cultivars of varying susceptibility. A. tumefaciens, strain B6, while morphologically similar to the chrysanthemum isolates, was less pathogenic to chrysanthemum, infecting approximately 50% of the cultivars which were infected by the chrysanthemum strain of the bacterium. Other isolates of the crown gall bacterium did not produce galls on chrysanthemum. A. tumefaciens is systemic in chrysanthemum. The bacteria moved upward and downward through the stems from the original inoculation sites, and were repeatedly recovered from inside stems, leaf petioles, and leaf midveins. Primary galls occurred at terminal pinches, the site of lateral shoot removal, or at sterile needle punctures on the stems, leaf petioles and leaf veins. Galls occurred only at the site of an injury if bacteria were present.