2019
Investigating SDS and Fusarium Root Rot Resistance, Preventative Seed Treatments, and Pathogen Variability in Kansas
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Contributor/Checkoff:
Kansas Soybean Commission
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Christopher Little, Kansas State University
Co-Principal Investigators:
Project Code:
1948
Contributing Organization (Checkoff):
Kansas Soybean Commission
$39,950
Institution Funded:
Kansas State University
$39,950
Brief Project Summary:

Sudden death syndrome is a perennial cause of yield loss across the Midwest. It is caused by the soilborne pathogen, Fusarium virguiliforme. SDS also can weaken the host, making it more susceptible to abiotic stresses (e.g. drought), pest infestation, and other diseases. Fusarium root rot causes perennial yield losses in Kansas and represents an underexplored group of pathogens in the state. Many of the same Fusarium pathogens cause seedling disease. Project objectives include screening adapted Kansas germplasm, plant introductions for resistance using high-throughput methods; examining the effect of seed treatment fungicides; and determining pathogenic variability of F. virguiliforme from multiple Kansas fields.

Key Benefactors:
farmers, breeders, plant pathologists

Information And Results
Final Project Results

Update:
FINAL REPORT*,**
(*Objectives are ongoing in the 20-21 Fiscal Year)
(**Report delayed to COVID-19 restrictions to University office and lab access.)

Sudden death syndrome (Fusarium virguiliforme) is an important disease that affects soybean yields across the United States every year. The pathogen survives in the soil where it starts infection on soybean roots as root rot. After root colonization, F.v. produces a toxin that spreads throughout the plant that kills the vascular system, which in turn, cuts off the plants' water supply. Because SDS impacts soybean yields, it is important to understand how the disease is spread to understand how to control it. Natural resistance to both the toxin and root phases of the pathogen differs among varieties of soybeans.

Objective 1. Screen adapted Kansas germplasm and KSVT entries for SDS resistance using three high-throughput methods.

This objective has been the primary effort area of the KSC-funded work and was a continuation from the 2018-2019 project and overlaps with the final report for last year’s project. Germplasm has been screened using three methods: (i) culture extract/toxin assay method, (ii) rolled-towel method, and (iii) layer-cake method. Additionally, a subset of 20 lines from Dr. Schapaugh’s program, which have undergone cut-stem assay screening, rolled towel, and layer cake screening were screened in the field (Rossville, Kansas) for SDS reaction and AUDPC (area under the disease progress curve).

The toxin assay has been completed for both the Kansas Soybean Variety Trial (KSVT) and the entries from Dr. Schapaugh's program (KS# breeding entries). During 20-21 some of these lines will be retested. The rolled-towel assay has been completed for the KSVT and a subset KS# breeding entries. The layer-cake screening has been completed for a subset of the KSVT and KS# breeding entries. Summarized data is available in table form in the attached PDF. The KSVT was not screened in the field for SDS, however a subset of KS# entries have been screened in the field. This subset is used to relate the efficacy of the assays to field data. As experiments are repeated, data is updated and being written as a formal research paper to submit to a peer-reviewed plant pathology journal.

As previously mentioned, the simple rolled-towel pathogenicity assay has the potential to predict SDS field severity for soybean genotypes. In other words, entries that are rated as resistant in the rolled-towel assay are rated resistant in the field a larger proportion of the time, compared to the toxin (cut-stem) and layer-cake assay. The ultimate dependability of this association will be something that will continue to be worked out during the 20-21 project.

Objective 2. Examine the effect of seed treatment fungicides on F. virguiliforme colonization of seedlings and colonization by other pathogenic Fusarium spp.

Active ingredients including azoxystrobin and fludioxonil are being tested against soybean root-associated Fusarium spp. See attached PDF for an example of fludioxonol sensitivity testing of Fusarium isolates. This work is ongoing and will continue into the next year of the project. Unfortunately, due to COVID-19 restrictions, access to lab activities has been limited/restricted in spring 2020 when these experiments were planned.

Objective 3. Determine pathogenic variability of F. virguiliforme isolates from multiple Kansas fields.

F. virguilforme isolates are being collected from soil, soybean residue, and symptomatic plants throughout the affected soybean production areas of Kansas as possible. Other root-associated Fusarium spp. will be isolated from asymptomatic and symptomatic plants. Strains are isolated into pure culture and single-spored for long-term storage. See the 20-21 proposal for more detail.

Sample collection locations for strains of F. virguiliforme include Manhattan, Rossville, Silver Lake, Belleville, Scandia, and Columbus, KS. Locations from additional fields in various Kansas counties have been added and will be added later this summer during the 20-21 project as more symptomatic fields appear. Also, we have initiated a collaboration with Plant Disease Diagnostic Lab at K-State to obtain additional samples for isolate collection from those that come in from around the state, further widening our collection scope.

View uploaded report PDF file

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.