1a. Objectives (from AD-416):
The long-term objective of this program is to develop biologically based technology for controlling soilborne pathogens of wheat, barley and brassica crops, grown as part of cereal-based production systems. Three specific objectives will be addressed over the next five years. Objective 1: Evaluate the pathogenic diversity, host range, and geographical distribution of fungal and nematode root pathogens, and the influence of cropping systems on soilborne diseases. Objective 2: Characterize microorganisms and mechanisms active in suppression of soilborne diseases. Objective 3: Identify and characterize molecular mechanisms of host-microbe interactions, including the action of host genes governing disease resistance and biological control.
1b. Approach (from AD-416):
Biological control of soilborne fungal pathogens such as Gaeumannomyces, Rhizoctonia, Pythium, Fusarium and nematodes by naturally-occurring and genetically-altered microorganisms will be developed and quantified in agricultural soils. Molecular approaches will be used to detect and quantify soilborne pathogens and their microbial antagonists, and to characterize microbial communities in bulk soil and the rhizosphere. Genetic determinants and molecular mechanisms responsible for root colonization and pathogen suppression will be characterized with emphasis on the genetics and regulation of phenazine and phloroglucinol biosynthesis in vitro and in situ. The genetic and physiological diversity of populations of root pathogens and their microbial antagonists, and influence of cropping systems on pathogens and antagonists will be determined. Genomes of pathogens and antagonists will be analyzed. New sources and mechanisms of host resistance will be identified. Practical disease control will be accomplished by maximizing the activity of natural biocontrol agents.
3. Progress Report:
Most wheat, barley and biofuel crops are infected by soilborne fungal pathogens and parasitic nematodes that reduce yields 10-30% annually. Diseased crops cannot take full advantage of fertilizers and irrigation water, and unused nitrates move into surface and ground water. The goal of this project is to develop biologically-based technology for controlling root diseases of wheat, barley and biofuel brassica crops. Progress was made on all three objectives and their subobjectives, all of which fall under National Program 303 and encompass Component 1 Problem 1, Component 2 Problem C, or Component 3 Problem B. Under Objective 1.A, we made significant progress in the development of a molecular assay for detection of the lesion nematode in soil. This research aligns with Components 1 because it describes an assay that allows rapid detection and quantification of this nematode and an assessment of risk prior to planting. Under Objectives 1.A and C, we made significant progress in identifying the distribution of the lesion nematode in dryland wheat fields and showed that populations were positively correlated with spring precipitation and negatively correlated with summer temperature. This research aligns with Component 2 Problem C because it provides new fundamental information about the ecology and epidemiology of lesion nematode, helps growers with management decisions, and prevents the unnecessary waste of inputs such as fertilizer that will not solve the problem. Under Objective 2.A, we made significant progress in identifying large, unique, widespread and genetically diverse populations of phenazine-producing bacteria on the roots of dryland wheat and showed that these bacteria can suppress root-rotting pathogens that are a major constraint to wheat production. This research aligns with Component 3 Problem B because it identifies a naturally occurring group of bacteria on wheat roots that can suppress soilborne diseases. Under Objective 1.B, we made significant progress in identifying the geographic distribution of groups of pathogenic Rhizoctonia in wheat and barley fields and showed that some groups are cosmopolitan and other are more confined to certain agronomic zones. This research aligns with Component 2 Problem C because it shows how precipitation and management practices can impact the biogeography of important pathogens of cereal, grain legume and biofuel crops in the Pacific Northwest.
Weller, D.M., Mavrodi, D., Van Pelt, J.A., Pieterse, C.M., Van Loon, L.C., Bakker, P.A. 2012. Induced systemic resistance (ISR) in Arabidopsis thaliana against Pseudomonas syringae pv. tomato by 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens. Phytopathology. 102(4): 403-412.