Soybean sudden death syndrome (SDS), caused by Fusarium virguliforme, is one of the most yield limiting diseases in the US, and effective disease management options are limited. We developed a realtime quantitative PCR assay for the diagnosis and quantification of F. virguliforme. Using this assay we investigated the F. virguliforme infection process of four soybean cultivars with differing resistance to the foliar SDS leaf scorch symptoms. We found that the quantity of F. virguliforme did not differ between the varieties as expected, indicating that leaf scorch resistance is separate to root infection resistance. Interestingly the ratio of F. virguliforme to soybean increased sharply just before the R5 growth stage, around the time of foliar disease onset. The findings also demonstrate that use of a soybean variety with resistance to the SDS foliar scorch will not necessarily reduce the subsequent amount of F. virguliforme in the soil.
Soil Science Extension
University of Wisconsin Madison