Determinants of aggressiveness in Fusarium graminearum
There are plant pathogen variants (races or pathotypes) that diverge on their aggressiveness or their ability to cause disease. This aggressiveness is genetically controlled, and identifying the genes that control this variation will help develop precision disease management techniques. We reported that Fusarium head blight in Illinois is caused by only one of the populations known to occur in North America irrespective of the level of resistance of the wheat line. We also identified F. graminearum genes that are differentially expressed between strains that infect wheat lines with different levels of resistance and genes highly expressed on all wheat varieties.
Determinants of virulence in Setosphaeria turcica
S. turcica, the causal agent of Northern corn leaf blight also presents strain variants that differ in their ability to cause disease on corn and on sorghum. For this pathogen, we have validated genetic markers for specific virulence genes. We reported that critical pathogenicity genes are genetically linked with the ability of the pathogen to grow in vitro. These results suggest a fitness cost for the pathogen to overcome two resistance genes of maize. In practical terms, it means that producers can rely on those resistance genes to provide durable resistance. We continue this project by creating and phenotyping a biparental population of the pathogen. We found that these genes are not associated with previously identified virulence genes nor close to fitness-related genes.
Detection and characterization of soybean foliar pathogens
One critical piece of information for managing a disease is if it causes a yield effect on its host. We created a linear model that predicts yield losses based on the disease progress of Septoria brown spot of soybean. We also developed and validated a quantitative PCR methodology to identify and quantify Septoria glycines on soybeans. In addition, we are currently finishing a report on the changes of the fungal soybean phyllosphere microbiome due to infection with Septoria and the application of fungicides.
Characterization and management of soybean seedling diseases
We evaluated the effect of novel seed treatment with multilocation field trials in combination with lines with diverse resistance types against Phytophthora root rot of soybean. Our findings showed a positive effect for soybean stands thanks to the seed treatment, but the yield effects were only observed on fields with high disease pressure. We are also finalizing the report of a characterization of the Illinois isolates.