Fungal pathogens can be very damaging to soybean (Glycine max (L.) Merrill) production reducing both yield and quality. Environmental conditions can increase disease severity and favor the spread of certain pathogens. In the Mid-Atlantic, we continue to observe extreme weather events and periods of prolonged rainfall that can lead to widespread fungal infection and reduced seed quality. A survey was established in 2019 to document which soilborne pathogens are most commonly observed across the region. This research identified numerous fields with Charcoal rot caused by Macrophomina phaseolina and fields with various diseases caused by the Phomopsis/Diaporthe
complex.

This project continues efforts from the 2019 survey by targeting Mid-Atlantic soybean farms with history of disease based on surveys and correspondence facilitated by the 2019 research. Certain fungal species can be difficult to separate by morphology alone and molecular tools offer a way to confirm proper identification.

Knowing the correct identity of a pathogen is important for management recommendations regarding variety selection or fungicide program. Pathogens isolated from this project will be analyzed using molecular techniques to increase our understanding of soilborne fungal pathogen distribution across Delaware fields.

1. Build a collection of isolates from Mid-Atlantic soybean fields with history of soilborne fungal disease.
2. Observe the frequency of isolation within and across farms and characterize fungal isolates to species using molecular protocols.
3. Share research findings through extension events and use findings to inform future management trials.

Updated July 27, 2020:
At this time, 15 survey sites have been identified to build fungal isolate collections. Early season isolates have been collected from five farms and the additional 10 sites will be surveyed in August and September. Fungi isolated to date are in pure culture and will be prepped for DNA extraction, PCR amplification, and sequencing in September/October once the full isolate set has been collected. Through morphological ID, we have collected fungi from the genus Diaporthe (causal agents of pod and stem rot, stem canker, etc.), Fusarium, and Macrophomina (charcoal rot). We have also collected Oomycete pathogens Pythium (Pythium root rot) and Phytophthora (Phytophthora root and stem rot). These will be identified to species using molecular methods mentioned above.

Updated January 29, 2021:

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Soilborne pathogens can reduce soybean yield and quality. Limited research has been conducted in recent years to characterize and identify problematic fungal pathogens to species. Project objectives included: 1) Build a collection of isolates from Mid-Atlantic soybean fields with history of soilborne fungal disease. 2) Observe the frequency of isolation within and across farms and characterize fungal isolates to species using molecular protocols. 3) Share research findings through extension events and use findings to inform future management trials. In 2020, twenty-eight field sites were surveyed. Diaporthe longicolla was the dominant pathogen identified in 2020. From this trial, an isolate collection was established that will be used in greenhouse and field screening trials in 2021.