Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2013
Publication Date: 9/24/2013
Citation: Okubara, P.A., Mavrodi, O., Maketon, C., Walter, N., Aly, H., Taylor, C. 2013. Pseudomonas-based approaches for suppression of soilborne pathogens and pests. Meeting Proceedings. Full Papers Proceeding Book, p.61-72. Interpretive Summary:
Technical Abstract: Soilborne necrotrophic fungal and oomycete pathogens, together with plant-parasitic nematodes, account for billions of dollars in yearly losses to agriculture in the US and worldwide. Introduced biopesticide strains of Pseudomonas appear to have limited application in the dryland wheat production regions of the Pacific Northwest, USA (PNW). However, we seek to augment current management of both soilborne fungal and nematode pathogens in wheat cropping systems by generating molecular information about how biocontrol strains of Pseudomonas impact wheat root defense gene expression. The long-term goal of this research is to enhance root defense gene expression, possibly in the absence of the biopesticide. Our findings indicate that the biopesticide Pseudomonas fluorescens strain Q8r1-96 induces several sets of genes in wheat roots that are associated with plant innate immunity pathways. The pathways include oxidative stress, the hypersensitive response and jasmonic acid signaling. In addition, possible detoxification of Pseudomonas-derived metabolites has been implicated. The likelihood of modulating innate immunity for better suppression of necrotrophic fungal pathogens is discussed. We have also characterized newly-isolated Pseudomonas strains suppressive to several species of fungal and nematode pathogens, with the view sequencing the genomes of selected strains. Our hypothesis is that the genome sequences will reveal new bacterial loci encoding the suppressive factors, thereby providing leads for the development of synthetic fungicides or nematicides, or for bacterial genes that can be up-regulated on or in host plant roots for more consistent pathogen suppression. Inhibition of Meloidogyne incognita, Heterodera glycines, Rhizoctonia solani AG-8, R. oryzae, Pythium ultimum and P. irregulare group I is summarized.