Updated July 4, 2018:

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EFFECT OF SOYBEAN CYST NEMATODE ON FUSARIUM
ROOT ROT OF SOYBEAN

EXECUTIVE SUMMARY
NORTH DAKOTA SOYBEAN COUNCIL
JUNE, 2018

Dr. Berlin D. Nelson Jr., Principal investigator, Plant Pathology, NDSU
Dr. Hui Yan, Research Scientist, Plant Pathology, NDSU

Fusarium root rot caused by F. solani and F. tricinctum are two serious root rot pathogens of soybean in North Dakota. Although Fusarium is common in soybean roots, it does not always cause yield losses. Healthy, well growing plants can produce new roots and compensate for the loss of decayed roots. Plants are more likely to suffer from Fusarium root rot when there is a high level of pathogen in the soil, and when plants are stressed by environmental factors such as lack of water, high temperatures or biological factors such as presence of other pathogens. Soybean cyst nematode (SCN) is common in many ND soybean fields. SCN causes wounds as they penetrate the roots and they change the physiology of the root while feeding. The nematode therefore could increase the damage caused by Fusarium root rot. The goal of this research was to determine if the presence of soybean cyst nematode in the soil with these Fusarium pathogens will result in greater damage to the plant than caused by the Fusarium pathogens alone.

Greenhouse and field studies were conducted over two years to investigate this potential problem. The results indicated when levels of Fusarium are high and environmental conditions are conducive for root rot, the addition of SCN to the soil will generally have no effect on damage to the plant because Fusarium root rot will have destroyed much of the roots, or even killed the plant. Live roots are needed for SCN to actually affect plant growth. However, when the Fusarium levels are low to moderate and root rot is less severe, the addition of SCN to the soil can result in greater damage to the plant compared to plants growing with SCN alone or Fusarium alone. These results are more likely to occur at higher than lower SCN egg levels in soil. Growth characteristics such as plant height and weight can all be reduced by the addition of SCN in the presence of some root rot. Also, the severity of Fusarium damage on the roots can be increased by SCN.

In conclusion, at low levels of Fusarium inoculum and moderate to high egg levels of SCN, the interaction of these two pathogens can reduce plant growth and increase root rot severity. Management of SCN should also focus on keeping egg levels low in infested fields to avoid interactions with soil borne fungal pathogens.


Effect of soybean cyst nematode (SCN) plus Fusarium root rot on growth of soybean. A is Fusarium solani (FSSC11) and B is Fusarium tricinctum (FT). The plant on the left side of each photo is a plant infected with both SCN and Fusarium. The plant in the middle is infected with only Fusarium and the plant on the right side is the uninfected plant (ck). The plant infected with both SCN and Fusarium is shorter and has a less of a root system than the plant infected with only Fusarium.