PARENT SESSION
Organized Oral Session 35: Mutualism, competition, and invasion: Applying ecological theory to agriculture
Organizer(s): LE Drinkwater, J Maul, DK Letourneau, and KL Monsen
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 511a, Level 5, Palais des congrès de Montréal
Recruitment of disease suppressive soil microorganisms through crop cultivation.
Mazzola, Mark*,1, Raaijmakers, Jos2, 1 USDA-ARS, Wenatchee, WA2 Wageningen University, Wageningen, The Netherlands
ABSTRACT- The impact of plant species on composition of soil microbial communities is accepted. There is emerging evidence that host genotype will have a significant influence on the structure and function of important elements of the saprophytic soil microbial community with the capacity to modulate development of soilborne plant diseases. Several accounts exist concerning the induction of disease suppressive soils realized as a result of continuous crop monoculture. One such example is the spontaneous decline in the incidence of take-all of wheat, a disease incited by the fungal pathogen Gauemannomyces graminis var. tritici, observed after one or two severe outbreaks of the disease in wheat monoculture production systems. A series of studies demonstrated that development of take-all decline is elicited, in part, via plant selection and enrichment of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. resident to soil ecosystems. In native soils, a state of take-all decline characteristically developed when 2,4-DAPG-producing fluorescent Pseudomonas spp. attained populations of approximately 105 cfu g-1 root. A similar level of disease suppression also was documented when an individual 2,4-DAPG strain was established at this population in a sterile soil system. The capacity to recruit functional populations of 2,4-DAPG-producers from the same resident bacterial community was wheat genotype-dependent. The dominant 2,4-DAPG producing genotype selected from resident populations was both soil and wheat-genotype dependent. This selection factor could be of significance to the development of take-all decline as certain 2,4-DAPG genotypes are superior rhizosphere colonists and thus provide a superior level of disease control. These data provide further evidence for the genotype-dependent capacity of plants to select for specific functional microbial communities. We postulate that selection of the appropriate plant genotype could substantially enhance recruitment of 2,4-DAPG producers from native soil populations and reduce the time period required for establishment of disease decline.
Key words: suppressive soil