Survival and Tumorigenicity ofAgrobacterium vitisin Living and Decaying Grape Roots and Canes in Soil

Abstract

Agrobacterium vitis was recovered from living and decaying grape roots and canes 23 months after grapes were artificially inoculated with a mixture of six strains of the bacterium. Each strain contained a unique plasmid profile. Following inoculation, some plants were treated with the herbicide Roundup to speed up plant death and tissue decay. Roots and canes were assayed over time, and by comparing plasmid profiles of recovered strains it was determined that certain A. vitis strains used in the inoculum mixture were recovered more frequently than others. Profiles identical to those identified for each strain used in the inoculum mixture were observed at least twice in strains recovered during the experiment. Of 133 plasmid profiles that were observed, only 18 did not resemble any of the strains used in the inoculum mixture. Of 333 strains recovered from roots and canes, 321 were tumorigenic, indicating that this trait was stable throughout the experiment. A group of six strains having plasmid profiles identical to strain CG49 that were recovered over an 16-month period were further characterized using restriction fragment length polymorphic analysis of plasmid DNA, random amplified polymorphic DNA analysis of total genomic DNA, and ribofingerprinting of a chromosomal region including 1,479 bp (99.5%) of the 16S rDNA, the intergenic spacer between 16S and 23S rDNA genes, and 132 bp of the 23S rDNA gene. All six strains were shown to be identical to CG49.