During 2004, Geraldton wax plants (Chamaelaucium uncinatum cv. BM Violet) from commercial greenhouses in La Plata, Argentina showed gall-like structures on collars and roots similar to those reported by Carsten et al. (2). No pathogenic fungi were associated with lesions. Bacteria isolated from galls grown on medium 1A and D1M agar yielded colonies typical of Agrobacterium sp. (4). Four isolates were selected for further study. All isolates were aerobic, gram-negative rods and produced 3-ketolactose, but did not produce alkali from l-tartrate or accumulate poly-β-hydroxybutyrate inclusions. The isolates were able to grow with 2% NaCl, at 35°C, and also on potato dextrose agar medium containing CaCO3 (4) but without acid clarification. Polymerase chain reaction analysis with primers VCF/VCR that amplified the expected 730-bp product of virC operon confirmed that all strains harboured a Ti plasmid (3,4). In addition, strains were screened for extrachromosomal DNA by the in-well lysis and electrophoresis procedure of Eckhardt with minor modifications as reported by Albiach and Lopez (1) and compared with strain Agrobacterium tumefaciens LBA 958, all Argentinean strains tested harbored a plasmid similar in size. Pathogenicity was verified on Geraldton wax and tobacco plants. Bacterial suspensions of each isolate (108 CFU/ml) were pricked into the stems. Control plants were pricked with sterile distilled water. Plants were maintained at 23 ± 3°C and symptoms were recorded after 45 days. Development of almost spherical, white-to-flesh-colored, rough, spongy and wart-like galls at the inoculation sites of the inoculated collars, stems, and trunks were registered. In Geraldton wax, as galls aged, they become dark brown to black, rough, and woody. Bacteria were reisolated from these galls fulfilling Koch's postulates. No lesions were observed on the controls. To our knowledge, this is the first report of A. tumefaciens on C. uncinatum in Argentina.
References: (1) M. R. Albiach and M. M. López. Appl. Environ. Microbiol. 58:2683, 1992. (2) E. Carstens et al. Plant Dis. 83:783, 1999. (3) H. Sawada et al. Appl. Environ. Microbiol. 61:828, 1995. (4) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society. St. Paul, MN, 2001.
