Seed News

Cyst Tech Soybeans Reduce Soybean Sudden Death Syndrome

Date Posted: March 17, 2011

By Dr. Ronald E. Secrist
Soybean breeder, <,b>Mark Seed Co., Perry, IA

Perry, IA -- In the fall of 2010, many farmers saw a plant disease called Sudden Death Syndrome (SDS) infect their soybean fields. Because of the damage to the soybean plant caused by SDS, these producers suffered yield losses of 30% or more. This disease is caused by a soil-borne fungus called Fusarium virguliforme that attacks soybean plant roots early in the growing season. Later during the reproductive stage of the soybean plant, the fungus continues to grow in the roots, eventually producing a toxin that is translocated up into the leaves causing foliar symptoms of interveinal chlorosis and necrosis.

As the disease progresses and the plant matures, the leaflets die and detach, leaving bare petioles that remain attached to plant stems. Symptoms become obvious by late August and lead to pod abortion and reduced number and size of seed. Often when SDS and Soybean Cyst Nematodes (SCN) are together in a field, SDS severity seems to be much stronger.

For a number of years we have been studying SDS both independently and with a team of researchers from one of the State Universities. We have come to a conclusion that will provide farmers a solution to reduce the devastation caused by the disease. Our observations indicate that soybeans grown in a Cyst Tech rotation exhibited near zero infestation with SDS as compared to an approximate 50% to 100% infestation in an adjacent area, that had over the years, been planted to soybean cultivars that possess the PI 88-788 type of SCN resistance. The patented Cyst Tech CTA/CTB rotation was developed to provide soybean growers a method to manage and reduce SCN populations without forcing a shift to increased SCN reproduction on PI 88-788 type of cyst resistance. What we have seen is that the Cyst Tech rotation also appears to greatly reduce the incidence of SDS.

SCN Race Shift

After planting a field to SCN resistant beans for a number of years, the nematodes in that field will adapt to grow on that type of SCN resistance. This is called a race shift. Imagine a population that changes or mutates into something slightly different so that it can still exist in an environment. That is what the Soybean Cyst Nematode does, usually shifting into races 1, 5, or 7. Most SCN resistant beans that are on the market today are resistant to races 3 and 14. Therefore, as races shift, the once resistant beans become susceptible to the SCN in the field and the nematodes multiply; making the situation worse.

The Cyst Tech program is a patented two-step rotation. The first year is planted to Cyst Tech A (CTA) creating an environment for the cysts to shift back to race 3 (a controllable race). The first year will normally not show much of a yield increase during the race shift process. The next rotation to beans in that same field is a Cyst Tech B (CTB) variety. This reduces the cyst count. As you reduce the count, your yield increases. As you continue rotation of CTA’s and CTB’s; the A’s control race shift and the B’s continue to reduce nematode populations until your counts are under control. Your soybeans can then reach their genetic potential according to land and management.

In one field, based on previous history of 12 years of Cyst Tech rotation, the SCN population has remained primarily a SCN race 3 or HG Type 0. The check area in the middle of the plot was planted similar to a corn and bean rotation; planting SCN resistant varieties year after year. This part of the field has shifted to a SCN HG Type 2.5.7 or Race 1. What was interesting is that this Race 1 area was the only place in the entire field that showed any signs of sudden death. Yield in the Cyst Tech portion of the field ranged from 119 to 60 bu/A compared to 35 bu/A yield in the SDS infected portion.

The hypothesis is that Sudden Death Syndrome is affected by the type of Soybean Cyst Nematode. Incidence of SDS is associated with the race of Soybean Cyst Nematode rather than the presence of it. Perhaps physical or physiological changes in the soybean root caused by the HG Type 2.5.7 of nematode serve as additional points for entry of soil borne pathogens such as the cause of SDS, Fusarium virguliforme.

From our data, it appears that the only way to reduce SDS is to control the race of the SCN. The logical conclusion is that if a grower continues to plant the PI 88-788 type of SCN resistant varieties, they can expect a higher levels of SCN and SDS in the future. Without the use of Cyst Tech to manage your SCN population, higher rates of SDS in the future will be experienced. Minimizing yield loss from SDS begins with managing SCN.

So in summary, it seems that what we call the “bad cysts”, which are races of cysts present in fields that are planted to resistant varieties seem to cause Sudden Death Syndrome. The fields that are planted to Cyst Tech varieties have, what we call, “good” cysts that don’t seem to promote Sudden Death Syndrome. The bottom line is that planting your soybean fields using the Cyst Tech system will help control Sudden Death Syndrome. We are excited to see what our research and test results will show in this growing season. For more information, please visit the web site at to view videos that further show and explain our observations.

___________________________________________________________ Dr. Ronald Secrist received his PhD in Plant Breeding from Iowa State University. During this time he released several soybean cultivars through MBS. In 1989, he joined Dairyland Seed Company as their Lead Soybean Breeder and Station Manager in Illinois. This station was at the fore front of Dairyland’s efforts to develop SCN resistant cultivars using both greenhouse and field screening techniques. Ron was responsible for developing many of the company’s successful SCN cultivars during the 1990’s. He started the Iowa Research Station for Dairyland in 1998 in Gilbert, IA. The major emphasis was for high yield soybeans. Every year farmers plant over a million acres of the cultivars Ron has bred. Six of the cultivars have been awarded patents and another two are patent-pending.

Ron joined Mark Seed because he is excited about Bringing Cyst Tech technology to the farmer. “I think Cyst Tech will revolutionize the way soybeans are produced. With the right genetics and management, 100 Bu/A soybeans are possible today.”

Mark Seed Company, headquartered in Perry, Iowa, is one of the fastest growing seed companies in the United States. Cyst Tech has been designed to control the major pest of soybean, Soybean Cyst Nematode, and to increase yield for soybean producers. Many soybean farmers have seen yield increases of 20% and more by using the Cyst Tech program.

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