Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 5/6/2018
Publication Date: N/A
Technical Abstract: In the Pacific Northwest of the USA, wheat is grown under a wide range of climatic conditions. Two broad-spectrum antibiotics, 2, 4-diacetylphloroglucinol (DAPG) and phenazine-1-carboxylic acid (PCA), produced in the rhizosphere by indigenous Pseudomonas spp. provide protection against soilborne pathogens in the field. Wheat grown with high precipitation or irrigation is susceptible to take-all disease, but a natural suppression, take-all decline (TAD), develops because of the buildup of DAPG-producing-P. brassicacearum during wheat or barley monoculture. Even after decades of exposure to DAPG, the pathogen has not developed resistance because the antibiotic attacks multiple basic cellular processes. Wheat cultivars respond differentially to TAD, providing growers a means to increase the level of take-all suppression. Pure DAPG, DAPG-producing pseudomonads and TAD soil induced systemic resistance (ISR) in Arabidopsis thaliana but DAPG-deficient mutants and pasteurized soil lacked ISR activity. Likewise, PCA-producing pseudomonads and dryland wheat field soils enriched in PCA producers showed ISR activity. Moreover, the PCA produced on roots promoted biofilm development under dryland conditions and likely also influenced crop nutrition and soil health in the field. DAPG- and PCA-producing pseudomonads are critical to the root health of small grains and other crops, but knowledge gaps remain about their interactions with the host, pathogens, phytobiomes and the environment. “Omics” technologies that allow characterization of the functional potential of microbial communities in unprecedented detail will undoubtedly shine light on previously unrecognized relationships among microbial consortia, plant hosts and pathogens, and disease suppression, providing insight into microbial community management strategies to enhance crop protection. The current industrial interest in biocontrol speaks to the important role that the technology is expected to play in 21st century agriculture, but much remains to be revealed to overcome the historic barriers faced in classical biocontrol research.