Updated December 6, 2019:
Seedling diseases rank in the top five threats to soybean because their insidious nature makes them difficult to diagnose and control. This project will determine the impact of environmental conditions on the epidemiology of seedling pathogens. Soybean producers will see benefits in the form of better management recommendations provided in a variety of formats. Soybean producers would also see their funding being maximized by the synergy of this team with the NCSRP Seedling Disease Project.

Objectives:
• Identify the effect of environmental conditions on the aggressiveness of seedling pathogens
• Identify field conditions (moisture, temperature and chemical properties) that favor seedling diseases
• Identify fungal and oomycete species associated with iron chlorosis
• Determine the effect of pH on the interaction of pathogens

Brief Summary:
New information on seedling diseases was made available in encyclopedia format on the Crop Protection Network website (www.cropprotectionnetwork.org). Seedling disease publications are being updated with new research information generated from the grant projects. Ongoing projects include developing new web resources in the coming months on seed treatments and seedling diseases, and creating press releases through SRII to highlight research accomplishments.

We characterized the isolates obtained between 2016-2018 from plants with and without iron deficiency chlorosis using DNA sequencing. We developed a manuscript on the effects of soil texture, pH, and soil moisture on seedling root rot caused by F. graminearum in greenhouse conditions.

Research demonstrated that isolation of oomycetes from soybean can depend on the tissue, location, year, and seed treatment. Additionally, seed treatments containing mefenoxam or metalaxyl and ethaboxam can be effective to reduce the probability of oomycete isolation from soybean roots.

Earlier reports during the project period indicated that F. equiseti is not a pathogen. However, it is a common resident of seeds, seedlings, and roots. High wind speeds, which can also create stress physical stress, were correlated to higher isolation frequencies of F. proliferatum. In this case, average daily windspeeds of > 8 mph, were associated with the highest recovery of F. proliferatum. This too could be due to plant stress or damage, a situation of which F. proliferatum could take advantage.

The impact of cover crops on seedling diseases of soybean were continued this season. In addition, the impact of fungicides on soybean seed health were investigated. Our results indicate that long-term tillage and fertilizers inputs not only affected soil physical and chemical characteristics, but were also significant determinants of bacterial, fungal, and oomycetes community structure. Soil microbial communities, including fungal species associated with seedling diseases, were found to be significantly affected by tillage and fertility treatments. Tillage treatment emerged as the main factor driving beta-diversity in soil microbial communities. The long-term tillage and fertility treatments resulted in varied ecological niches that selected for adapted microbial lifestyles that impacted crop productivity and soil health.