1a. Objectives (from AD-416)
The objective of this cooperative research is to identify, characterize and control soilborne pathogens of wheat and barley, such as Fusarium, Pratylenchus and/or Heterodera, which cause root and crown rot diseases; to identify the effects of cropping system on root pathogen populations and diversity, and on disease epidemiology; and to identify wheat germplasm with performance against root pathogens.
1b. Approach (from AD-416)
Root and crown rot diseases will be identified and characterized through a combination of laboratory, greenhouse and field studies. The ecology of root pathogens and effects of cropping system on pathogen populations and diversity, and disease epidemiology will be determined using classical plant pathology and microbiology methods and molecular techniques. Wheat germplasm will be screened for resistance or tolerance to root and crown pathogens in the field and greenhouse. Practical root disease control will be accomplished through a combination of agronomic practices, and biological and chemical treatments. Documents SCA with OSU. Replacing 5348-22000-013-02S 58-5348-4-464 (4/09).
3. Progress Report
As crop management practices change from an intensively cultivated to conservation systems the prevalence and severity of diseases may also change. ARS collaborators at Oregon State University, Pendelton evaluated diseases in long-term cropping system experiments in low-rainfall regions and found that yields of wheat is often inversely correlated with density of root-lesion nematodes. Nematode density was not affected by intensity of tillage but was much lower following barley compared to wheat, canola, mustard or pea. Extraction of water stored in the soil profile was inversely correlated with the density of the nematodes. These observations indicate a need to monitor and to reduce populations of root-lesion nematodes in wheat fields. Crop management recommendations were modified.Management of root-lesion nematodes continues to be based upon the identity of the species present in each field. Most commercial diagnostic laboratories do not identify individual species due to high cost and degree of difficulty. ARS collaborators at Oregon State University, Pendelton developed species-specific primers to detect Pratylenchus species of importance to dryland agriculture and developed a multiplexing assay of soil to enable each species to be quantified as well as identified from a single DNA extract using real-time PCR. Tests with naturally-infested soils demonstrated that the real-time procedures for P. neglectus and P. thornei provided more accurate results than conventional extractions and identifications of lesion nematode species. These molecular methods will become the standard approaches for identifying these nematodes. Two cereal cyst nematode species occur in Oregon, Heterodera avenae and Heterodera filipjevi. These species differ in the timing at which juveniles emerge from cysts and in their reactions to genes for resistance in wheat and barley. Accurate identification of these species is important for developing effective management strategies but commercial nematode diagnostic laboratories do not distinguish these species. ARS collaborators at Oregon State University, Pendelton used polymerase chain reaction (PCR) and restriction fragment-length polymorphism (RFLP) procedures to identify these species in infested soils, and are using the PCR-RFLP procedure to screen soil samples. Sites in Oregon were found to be infested with mixtures of H. avenae and H. filipjevi but only H. avenae was detected in most fields sampled in each state. Molecular methods are revolutionizing how pathogenic nematodes on cereals are being identified. Accomplishments from this project will align with Component 1, Problem Statement 1B,Components 2, Problem Statement 2C, Component 3 Problem Statement 3B and Component 4, Problem Statement 4a of NP 303. Progress on this project will be monitored by conversations with the collaborator at professional meetings, through conference calls and by visits to Pullman or Pendelton.