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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).