2016
Soybean pathogen fungicide sensitivity screening
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Contributor/Checkoff:
Michigan Soybean Promotion Committee
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Martin Chilvers, Michigan State University
Co-Principal Investigators:
Project Code:
1614
Contributing Organization (Checkoff):
Michigan Soybean Promotion Committee
(n/a)
Institution Funded:
Michigan State University
(n/a)
Brief Project Summary:

The objective of this proposal is to examine the efficacy of fungicides through testing for fungicide sensitivity (resistance). Data from these experiments will assist in the monitoring for fungicide resistance and selection of the most appropriate fungicides for disease control. We will also assess the role of the fungicide fluopyram for soybean cyst nematode control in field and greenhouse studies.
The proposal will also include the characterization and testing of Rhizoctonia solani strains for their pathogenicity and virulence to soybean seed and seedlings. This information can then be further used in the screening of germplasm and fungicides (not part of this proposal).

Unique Keywords:
#soybean diseases
Information And Results
Final Project Results

1. Screen oomycete (Pythium and Phytophthora species) for fungicide sensitivity, which will build on current efforts through the OSCAP (USDA) and USB/NCSRP projects.
We have developed a high-throughput 96-well fungicide sensitivity assay for oomycetes, Pythium, Phytophthora and Phytopythium. The assay allows for rapid determination of fungicide sensitivity across a larger number of strains than traditional agar plate tests. A manuscript has been drafted describing this assay and will be submitted sometime this year.
Eighty species of Pythium have been screened for their sensitivity to mefenoxam and Ethaboxam. This data will aid in the understanding of seed treatment efficacy and the placement of seed treatments for improved seedling disease management.
We trained two graduate students from Iowa State University on the use of the assay. We plan to use the assay for a current NCSRP/MSPC project on Phytophthora sojae and P. sansomeana in Michigan and other states.

2. Screen Fusarium virguliforme the causal agent of SDS and closely related species for fungicide sensitivity and baseline determination.
Please find below an abstract from a manuscript that is being published in Plant Disease:
Wang, J., Bradley, C.A., Stenzel, O., Pedersen, D.K., Reuter-Carlson, U., Chilvers, M.I. Accepted Sep 17, 2016. Baseline sensitivity of Fusarium virguliforme to fluopyram fungicide. Plant Disease XXX:XX-XX
Fluopyram, a succinate dehydrogenase inhibitor (SDHI) fungicide, was recently registered for use as a soybean seed treatment for management of sudden death syndrome (SDS) caused by Fusarium virguliforme. Although registered, and now used commercially, in vitro baseline fungicide sensitivity of F. virguliforme to fluopyram has not yet been established. In this study, the baseline sensitivity of F. virguliforme to fluopyram was determined using in vitro growth of mycelium and germination of conidia assays with two collections of F. virguliforme isolates. A total of 130 and 75 F. virguliforme isolates were tested using the mycelial growth and conidia germination assays, respectively, including a core set of isolates that were tested with both assays. In the mycelial growth inhibition assay, 113 out of 130 isolates (86.9%) were inhibited 50% by effective concentrations (EC50) less than 5 µg/ml with a mean EC50 of 3.35 µg/ml. For the conidia germination assay, 73 out of 75 isolates (97%) were determined to have an estimated EC50 of less than 5 µg/ml with a mean EC50 value of 2.28 µg/ml. In a subset of 20 common isolates that were phenotyped with both assays, conidia germination of F. virguliforme was determined to be more sensitive to fluopyram (mean EC50 = 2.28 µg/ml) than mycelial growth (mean EC50 = 3.35 µg/ml). Hormetic effects were observed in the mycelial growth inhibition assay as 22% of the isolates demonstrated more growth on medium amended with the lowest fluopyram concentration (1 µg/ml), as compared to the non-fluopyram amended control. It was not possible to determine EC50 values for nine out of 185 isolates (4.8%), as those isolates were not inhibited by 50% even at the highest fluopyram concentrations of 100 µg/ml for mycelial growth and 20 µg/ml for conidia germination inhibition assays. On the whole, the F. virguliforme population appears to be sensitive to fluopyram, and this study enables future monitoring of fungicide sensitivity.


3. Determine the efficacy of fluopyram on soybean cyst nematode in field and greenhouse screens.
Greenhouse trials were conducted to complement studies in the field. We were able to demonstrate that ILeVO was able to suppress SCN reproduction, but not eliminate the pest. A manuscript will be written to analyze and present the data.


4. Determine the pathogenicity and virulence of Rhizoctonia solani AG groups using seed and seedling assays.

We have collected and begun identifying Rhizoctonia solani strains collected throughout Michigan. These strains will be utilized to determine their pathogenicity and aggressiveness on soybeans using two assays a seed rot assay and a seedling root rot assays. Preliminary trials have been set up to fine-tune the screening assays.


5. Communication

Information from this study has been relayed to industry and to growers through winter and summer meetings. A YouTube video was recorded to summarize impacts from this project https://www.youtube.com/watch?v=47pk2Y8W3-I

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.