Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/29/2017
Publication Date: N/A
Technical Abstract: Long known as biocontrol agents, phenazine-1-carboxylic acid (PCA)-producing pseudomonads are widely distributed across dryland cereal cropping systems of the Pacific Northwest, USA. We investigated the effect of soil moisture on the population levels, diversity, and composition of rhizosphere microbial communities, and the mechanisms driving accumulation of PCA producers in arid soils. A field study run for 3 consecutive years in adjacent irrigated and dryland plots revealed the magnitude of changes in the wheat rhizosphere microbiome in response to soil moisture, temperature, and crop monoculture, and shed light on the impact of environmental factors on indigenous bacterial communities and phenazine production in situ. Related studies in mesocosms revealed that PCA biosynthesis genes were expressed under both dryland and irrigated conditions, that PCA persisted in soils with a half-life of 3 to 4 days, and that PCA-producing bacteria on dryland roots were associated with more robust biofilms than were colonies of an isogenic PCA nonproducer. Few colonies of either strain were observed on roots grown with irrigation. Biomass from 15N-labeled bacteria was transferred directly to roots when cells were not sheltered within biofilms. Collectively, these results indicate that PCA production is an adaptation to water stress that promotes the formation and development of root-associated biofilms, potentially influencing the availability of bacterial N to crops.