Quantification of Fusarium avenaceum in soil and crop residues from pea fields in Alberta

Root rot is a destructive disease of field pea on the Canadian prairies. One of the main pathogens involved in the root rot complex is Fusarium avenaceum. The objective of this study was to use real time PCR for quantification of F.avenaceum DNA in soil and crop residues collected from commercial pea fields. For this purpose, a specific primer and hydrolysis probe set was designed based on partial elongation factor alpha gene sequence. The assay was then used to quantify the pathogen in naturally infested samples collected from pea fields in Alberta. Soil, stubble (post-harvest pea) and straw (previous crop prior to pea seeding) samples was collected from field sites with and without root rot disease symptoms. The quantity of DNA detected in stubble and straw samples was relatively higher than that detected in soil samples, indicating the importance of crop residues as a source of inoculum for this pathogen. In order to correlate disease severity to inoculum levels, greenhouse experiments using different levels of F. avenaceum inoculum added to the soil was conducted and changes in disease severity recorded. Results showed that there was a positive relationship between these two factors. The outcomes from this study, combined with additional information about other pathogens involved in root rot disease and environmental parameters, will be applied toward developing a disease risk model.