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. 2004 May;70(5):2779-85.
doi: 10.1128/aem.70.5.2779-2785.2004.

Acquisition of an Agrobacterium Ri Plasmid and Pathogenicity by Other alpha-Proteobacteria in Cucumber and Tomato Crops Affected by Root Mat

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Free PMC article

Acquisition of an Agrobacterium Ri Plasmid and Pathogenicity by Other alpha-Proteobacteria in Cucumber and Tomato Crops Affected by Root Mat

S A Weller et al. Appl Environ Microbiol. .
Free PMC article

Abstract

Root mat of cucumbers and tomatoes has previously been shown to be caused by Agrobacterium radiobacter strains harboring a root-inducing Ri plasmid (pRi). Nine other pRi-harboring alpha-Proteobacteria have subsequently been isolated from root mat-infected crops. Fatty acid profiling and partial 16S rRNA sequence analysis identified three of these strains as being in the genus Ochrobactrum, five as being in the genus Rhizobium, and one as being in the genus Sinorhizobium: An in vitro pathogenicity test involving inoculation of cucumber cotyledons was developed. All pRi-harboring alpha-Proteobacteria induced typical root mat symptoms from the cotyledons. Average transformation rates for rhizogenic Ochrobactrum (46%) and Rhizobium (44%) strains were lower than those observed for rhizogenic A. radiobacter strains (64%). However, individual strains from these three genera all had transformation rates comparable to those observed from cotyledons inoculated with a rhizogenic Sinorhizobium strain (75%).

Figures

FIG. 1.
FIG. 1.
UPGMA dendrogram for fatty acid methyl ester data from a panel of RMA A. radiobacter strains, representative Agrobacterium spp., and rhizogenic α-Proteobacteria isolated from RMA crops.
FIG.2.
FIG.2.
Neighbor-joining phylogeny for partial 16S rRNA sequences (alignment length, 1,050 bp) showing relationships between rhizogenic α-Proteobacteria isolated from RMA cucumber and tomato crops as well as a panel of representative strains. Footnotes: a, numbers on the dendrogram represent the percentages of grouping confidence calculated by bootstrap analysis (100 bootstrap replicates); b, GenBank accession numbers; c, strains in bold are the nine rhizogenic α-Proteobacteria strains plus two rhizogenic A. radiobacter strains isolated from RMA cucumber crops.
FIG. 3.
FIG. 3.
Rooting from cucumber cotyledon inoculated with rhizogenic A. radiobacter strain (NCPPB 4042) 12 days postinoculation.

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