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Applied and Environmental Microbiology, May 2000, p. 1939-1946, Vol. 66, No. 5
Root Disease and Biological Control Research
Unit, USDA Agricultural Research Service, Washington State
University, Pullman, Washington,1 and
Department of Phytopathology, Wageningen Agricultural
University, Wageningen, The Netherlands2
Received 8 October 1999/Accepted 2 March 2000
Production of 2,4-diacetylphloroglucinol (2,4-DAPG) in the
rhizosphere by strains of fluorescent Pseudomonas spp.
results in the suppression of root diseases caused by certain fungal
plant pathogens. In this study, fluorescent Pseudomonas
strains containing phlD, which is directly involved in the
biosynthesis of 2,4-DAPG, were isolated from the rhizosphere of wheat
grown in soils from wheat-growing regions of the United States and The
Netherlands. To assess the genotypic and phenotypic diversity present
in this collection, 138 isolates were compared to 4 previously
described 2,4-DAPG producers. Thirteen distinct genotypes, one of which represented over 30% of the isolates, were differentiated by
whole-cell BOX-PCR. Representatives of this group were isolated
from eight different soils taken from four different geographic
locations. ERIC-PCR gave similar results overall, differentiating 15 distinct genotypes among all of the isolates. In most cases, a single
genotype predominated among isolates obtained from each soil. Thirty
isolates, representing all of the distinct genotypes and geographic
locations, were further characterized. Restriction analysis of
amplified 16S rRNA gene sequences revealed only three distinct
phylogenetic groups, one of which accounted for 87% of the isolates.
Phenotypic analyses based on carbon source utilization profiles
revealed that all of the strains utilized 49 substrates and were unable to grow on 12 others. Individually, strains could utilize about two-thirds of the 95 substrates present in Biolog SF-N plates. Multivariate analyses of utilization profiles revealed phenotypic groupings consistent with those defined by the genotypic analyses.
0099-2240/00/$04.00+0
Genotypic and Phenotypic Diversity of phlD-Containing
Pseudomonas Strains Isolated from the Rhizosphere of
Wheat
*
Corresponding author. Mailing address: Root Disease and
Biological Control Research Unit, USDA Agricultural Research Service, Pullman, WA 99164-6430. Phone: (509) 335-1116. Fax: (509) 335-7674. E-mail: mcspadde{at}mail.wsu.edu.
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