2021
Resistance to Important Soybean Diseases
Contributor/Checkoff:
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Berlin Nelson, North Dakota State University
Co-Principal Investigators:
Project Code:
QSSB
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:
In North Dakota there are important soybean diseases including Phytophthora, Fusarium and Rhizoctonia root rots, soybean cyst nematode and sudden death syndrome. This project will focus on identifying resistance to Phytophthora root rot and sudden death syndrome and incorporating resistance into adapted germplasm for this region through cooperation with the soybean breeder. Because sudden death syndrome is a new disease for North Dakota, resistant varieties have not been developed for this area. This project will identify sources of resistance in maturity groups for this region that can be used in the NDSU soybean breeding programs.
Key Beneficiaries:
#agronomists, #breeders, #farmers
Unique Keywords:
#germplasm, #sds, #soybean diseases, #soybean varieties, #sudden death syndrome
Information And Results
Project Summary

Soybean diseases can cause substantial yield losses and influence variety selection and crop rotation. In North Dakota there are important diseases of soybean such as Phytophthora, Fusarium and Rhizoctonia root rots, soybean cyst nematode (SCN), and a new disease recently identified in ND called sudden death syndrome (SDS). SDS is caused by a fungus Fusarium virguliforme that infects the roots and causes both a root rot and above ground foliar symptoms. This project will focus on identifying resistance to Phytophthora root rot and sudden death syndrome and incorporating resistance into adapted germplasm for this northern region through cooperation with the soybean breeder. These are two diseases where resistance is available within the soybean germplasm. The soybean breeder and I have worked together in the past incorporating various form of resistance to Phytophthora root rot into public soybean varieties. An established protocol was developed for testing breeding lines for resistance, usually to Phytophthora races 3 and 4, but sometimes to other races. Because sudden death syndrome is a new disease for ND, resistant varieties have not been developed for this area. This project will identify sources of resistance in maturity groups for this region that can be used in public or private breeding programs. We are currently working on improving our screening methods to identify resistance to sudden death syndrome under greenhouse conditions. This funding request is for three years to develop lines with resistance to sudden death syndrome.

Project Objectives

1. Screen NDSU breeding lines for resistance and identify lines with high levels of resistance to Phytophthora root rot.
2. Screen adapted soybean germplasm for resistance to sudden death syndrome and identify sources of resistance that breeders can use in the development of resistant varieties for this area.

Project Deliverables

1. Identification of soybean breeding lines with high resistance to Phytophthora root rot.
2. Identification of sources of high levels of resistance to sudden death syndrome in maturity groups for this area.

Progress Of Work

Update:
Resistance to Important Soybean Diseases
Midyear progress report, December 1, 2020
Berlin D. Nelson Jr.

The primary objectives of this research are to identify sources of resistance to major soybean pathogens such as Fusarium virguliforme and Phytophthora sojae and screen NDSU breeding material for resistance to major pathogens.

In August of 2020 a survey for sudden death syndrome (SDS) was conducted in soybean fields in Richland County to determine if the disease has spread since it was first identified in 2018. This was conducted in areas around where the first field with SDS was found in August 2018. In the 2019 survey, we did not find any new fields with symptoms. The 2020 survey covered an area of approximately 400 square miles which was about 28% of the county. Some fields within this area were brought to the attention of the survey crew by crop scouts working in the area. Plants with typical SDS symptoms were collected from fields and the DNA was extracted from root tissue. The DNA was then tested for evidence of Fusarium virguliforme by PCR analysis using F6-3 and R9 primers specifically for this pathogen. Positive and negative controls were used in the analysis. The PCR test verified 12 fields in Richland Co. were positive for SDS. In addition, a field in Cavalier County, ND, was also observed with SDS symptoms by extension agents in the area and plants were sent to be analyzed using PCR. That field was also verified to have SDS. Although most of the fields observed in this survey had small patches of plants showing foliar symptoms of SDS, several of the fields had large areas with symptoms. The results from this research point out that SDS is a potential future problem for soybean growers in North Dakota. The disease is now well established in the area and because this is a soil borne pathogen, it will readily spread from field to field by agricultural equipment and the natural movement of soil by environmental conditions. It will be important that growers, crop scouts, and others managing soybean fields can identify this disease when it first appears. An important management tool that will likely be needed in the future will be SDS resistant soybean varieties.

In May of 2020, we initiated a field experiment to test the resistance of soybean varieties/plant introductions for resistance to sudden death syndrome. This was part of our effort to identify sources of SDS resistance that the NDSU breeding program could use in development of SDS resistant lines. We identified seven SDS resistant and three susceptible varieties from published research with seven of them in maturity groups I and 0. Five of the resistant varieties (MN302, Evans, Merit, P15A and P19A and three susceptible varieties (Spencer, Barnes and McCall) were planted into soil infested with F. virguliforme in large plastic pots. The inoculum (isolate P10-2 from North Dakota) was wheat seed colonized by the pathogen over three weeks, then mixed into La Prairie silt loam. The pots were buried in Fargo clay with part of the bottom removed so roots could grow into the soil under the pots. There were ten seeds per pot with four replications. A known SDS positive control (isolate 13FV mol) was included in the test on Barnes. There were ten seeds per pot and four replications per soybean variety. A non-inoculated control for each variety was included in the test. Emergence was recorded at 9 days following planting, the number of plants with the first true leaves were counted at 16 days and the number of plants with the second trifoliate leaves were counted at 21 days. Then plants were thinned to 6 plants per pot. Plants were watered each week for 6 weeks to maintain high soil moisture and promote SDS infection and disease development.

The results of the field tests showed that soil infested with F. virguliforme significantly reduced germination on some varieties and retarded plant growth. The resistant varieties P19A and MN0302 had the highest germination in the infested soil compared to the other varieties. P19A averaged 9 plants per pot while Spencer, the susceptible, averaged 3.5 plants per pot. P19A also had the greatest number of plants with true leaves after 16 days. The SDS resistant varieties, however, did not have the highest number of plants with the second trifoliate leaves after 21 days. At 7 weeks following planting, infected plants that were still growing averaged six inches shorter than those growing in non-infested soil. All plants were monitored for foliar symptoms throughout their growth, but typical foliar SDS symptoms did not develop in this experiment. The reasons for that are unknown. Plants were harvested on October 7 and the number of pods and the seed weights per plant were determined. P19A and Evans had the highest number of pods per plant and P19A had the highest seed weight per plant in the inoculated plants. In the uninoculated plants, P19A also had the greatest number of pods per plant and the highest seed weight. The results, however, were mixed in the inoculated plants as the SDS resistant varieties did not always trend toward higher yield compared to the susceptible varieties. The resistant varieties tended to have a lower percentage of root rot on the tap root compared to the susceptible varieties Barnes and McCall.

During the summer of 2020 soil was collected from 147 soybean fields in nine counties of SE North Dakota to initiate a study on the virulence of Phytophthora sojae, the cause of Phytophthora root rot of soybean. This soil is stored in the greenhouse and will be used to bait P. sojae from soil and then test virulence of the isolates on a set of eight differential cultivars. In the summer of 2021, soil will be sampled from other soybean producing counties. This information has a direct impact on the types of resistance that will be needed in future soybean varieties for North Dakota.

Final Project Results

Update:

View uploaded report Word file

Resistance to Important Diseases

FY 2021 Executive Summary for ND Soybean Council
June 30, 2021

Principal Investigator: Dr. Berlin D. Nelson Jr., Plant Pathology, NDSU
Cooperators: Dr. Carrie Miranda, NDSU Soybean Breeder, Plant Sciences.
Dr. Sam Markell, NDSU Extension Pathologist

A major focus of this research is to identify new soybean diseases or changes in pathogens that could threaten soybean production in North Dakota. In addition, we conduct research on ways to improve disease management. In cooperation with Dr. Miranda, the soybean breeder, we screened 148 advanced breeding lines for resistance to races of Phytophthora sojae, the cause of Phytophthora root rot. Most of the screening was for Race 4 resistance and over 66% of the lines tested were resistant to Race 4. One of the breeding lines resistant to race 4 was released by Dr. Miranda in 2021 as ND21008GT20 a glyphosate tolerant soybean.

In August of 2020 we continued efforts to find out if sudden death syndrome (SDS), a new disease for North Dakota, had spread in Richland Co where we first found it in 2018. SDS is caused the soil borne fungus Fusarium virguliforme. We surveyed an area of approximately 400 square miles and we identified 12 soybean fields with classic symptoms of SDS. In addition, extension agents in Cavalier Co. found a field close to the Canadian border with SDS symptoms and sent in plant roots for examination. With molecular techniques the presence of the pathogen was verified in all these fields. The results from this research point out that SDS is a potential future problem for soybean growers in North Dakota. The disease is now well established and because this is a soil borne pathogen, it will readily spread from field to field. It will be important that growers, crop scouts, and others managing soybean fields can identify this disease when it first appears. An important management tool that will be needed in the future will be SDS resistant soybean varieties. Currently, in our maturity groups, there are no commercial cultivars with known resistance to SDS.

A large effort has been underway to develop methods to identify resistance to SDS and identify sources of resistance that can be use in the NDSU soybean breeding program. There are sources of SDS resistance in the soybean germplasm, but there are few sources of resistance in adapted germplasm in maturity groups (MG) 0 and 00. Both greenhouse and field experiments have been conducted over the past year to improve our screening methods and find high levels of resistance in maturity group 0. Thus far we have found moderate levels of SDS resistance but not high levels in MG 0. More studies are in progress to identify additional sources of resistance.


Figure 1. Greenhouse testing for resistance in soybean to sudden death syndrome (SDS). Plants showing strong chlorosis had classic symptoms of SDS while more resistant varieties still had green leaves (March 30, 2021).


Benefit To Soybean Farmers

This is long term research which will benefit growers in the years to come when sources of resistance are incorporated into public and commercial soybean varieties. Resistance is the most valuable management tool for preventing major losses to important soybean diseases. To illustrate the importance of just one disease, in the United States in
2007 sudden death syndrome was estimated to cause losses of 22 million bushels of soybean.

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.