Diseases Rob Soybean Plants

The two plants on the left show the reduced growth of the roots due to the presence of Soybean Cyst Nematode, while the plant on the right shows normal growth in the absence of Soybean Cyst Nematode. Image is provided by North Dakota State University.

Soybeans have been cultivated in various regions around the world for thousands of years, and is currently a multi-billion-dollar industry. Today this plant, which is a great source of protein and essential amino acids, is consumed by millions of people and livestock around the world. Additionally, there are numerous other products derived from soybeans. Due to the versatility of how soybeans are used, coupled with the high demand for soybeans, it has become an important contributor to the economy.

This image shows WWF’s data for the global soy production in 1996, 2004, and 2012. A prediction of the global soy production is given for 2050.

Unfortunately, soybean plants are being attacked by a various pathogens and parasites, including over 50 genera of nematode species. Soybean Cyst Nematode (SCN), Heterodera glycines, however, is the most detrimental to the crop. This parasitic roundworm invades at the roots of the plant, hindering the plant’s ability to utilize water and nutrients, thus ultimately causing a reduction in the size of the plant. This reduction in growth leads to declined yields for farmers, which causes huge a economic loss of up to billions of dollars annually.

Where did SCN originate and how did it become a global issue?

The first case of SCN was reported in Japan in 1915, but based on later readings of ancient Chinese literature, it was found that SCN could have been a possible parasite effecting soybean crops in China as early as 235 B.C. After the reported encounter in Japan, SCN was found in Korea in 1936, Manchuria in 1938, United States in 1954, Taiwan in 1958, Egypt in 1968, and Canada in 1987. Expansion of SCN cases were documented in Colombia, Argentina, and Brazil around the 1980’s. As of 2016, there are reports of SCN in Africa, Asia, North America, and South America.

In the United States, the first documented report was in Hanover County, North Carolina in 1954. It has been hypothesized that the source of SCN was from a shipment of flower bulbs from Japan. After careful analysis of the disease in North Carolina and Japan, there was support found for this hypothesis, due to the very similar symptoms experienced by both plants. Spread of SCN was rapid in the United States, moving to most of the soybean producing states. The proposed modes of transmission of SCN include via contaminated seeds, contaminated farming tools/machinery, birds, wind, flood waters, animals, and farm workers.  

This animated GIF provides a visual representation of the spread of SCN from 1954 to 2014.
This figure, provided by Iowa State, shows the distribution of SCN (in red) and the soybean-producing counties in the United States, as of 2014.

Soybean Cyst Nematodes is becoming a huge infestation issue, because the world’s dominant producers of soybeans include the United States, Brazil, Argentina, and China. Cumulatively, these four countries make up 85% of the world’s total soy production. With this globally traded commodity being targeted by SCN, it is fundamental that we determine the best strategy to combat/manage SCN and implement it in the cultivation of soybeans.






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