Distribution and Biocontrol Potential of phlD+ Pseudomonads in Corn and Soybean Fields
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Date
2005
Journal Title
Journal ISSN
Volume Title
Publisher
Biological Control
Abstract
The abundance and diversity of phlD+ Pseudomonas spp. colonizing
the rhizospheres of young, field-grown corn and soybean plants were
assayed over a 3-year period. Populations of these bacteria were detected
on the large majority of plants sampled in the state of Ohio, but
colonization was greater on corn. Although significant variation in the
incidence of rhizosphere colonization was observed from site to site and
year to year on both crops, the magnitude of the variation was greatest for
soybean. The D genotype was detected on plants collected from all 15
counties examined, and it represented the most abundant subpopulation
on both crops. Additionally, six other genotypes (A, C, F, I, R, and S)
were found to predominate in the rhizosphere of some plants. The most
frequently observed of these were the A genotype and a newly discovered
S genotype, both of which were found on corn and soybean roots
obtained from multiple locations. Multiple isolates of the most abundant
genotypes were recovered and characterized. The S genotype was found
to be phylogenetically and phenotypically similar to the D genotype. In
addition, the novel R genotype was found to be most similar to the A
genotype. All of the isolates displayed significant capacities to inhibit the
growth of an oomycete pathogen in vitro, but such phenotypes were
highly dependent on media used. When tested against multiple oomycete
pathogens isolated from soybean, the A genotype was significantly more
inhibitory than the D genotype when incubated on 1/10× tryptic soy agar
and 1/5× corn meal agar. Seed inoculation with different isolates of the A,
D, and S genotypes indicated that significant root colonization, generally
in excess of log 5 cells per gram of root, could be attained on both crops.
Field trials of the A genotype isolate Wayne1R indicated the capacity of
inoculant populations to supplement the activities of native populations so
as to increase soybean stands and yields. The relevance of these findings
to natural and augmentative biocontrol of root pathogens by these
bacteria is discussed.
Description
Keywords
Biogeography, DAPG
Citation
McSpadden Gardener, BB, Gutierrez, LJ, Joshi, R., Edema, R., & Lutton, E. (2005). Distribution and biocontrol potential of phlD+ pseudomonads in corn and soybean fields. Phytopathology , 95 (6), 715-724. DOI: 10.1094/PHYTO-95-0715