Pioneer Provides Growers More Options for High-Yielding, SCN-Resistant Soybeans

New varieties help growers battle SCN as it spreads into northern areas

Soybean growers now have more options when selecting soybean varieties that have high yield potential and the ability to stave off soybean cyst nematodes (SCN). Pioneer Hi-Bred, a DuPont business, continues to expand its lineup of SCN-resistant soybean varieties, providing growers a choice in rotating SCN sources in their fields to keep potential resistance issues in check.

Soybean cyst nematode, the single most damaging pest of soybeans in the United States, continues to move northward from the southern U.S. and has reduced yields on tens of millions of soybean acres. All major soybean-producing states are affected, and the economic impact is more than $1 billion every year.

Using Multi-Sources for SCN Resistance to Maintain Effectiveness
“SCN cannot be eradicated from a field, even when soybeans are removed from the rotation,” says Jeff Thompson, research scientist for Pioneer in Mascoutah, Ill. “This means the goals for soybean growers are to maintain soybean yield, reduce SCN numbers and preserve the effectiveness of resistance soybean varieties.”

Just as alternating herbicides with different modes of action helps prevent weed resistance from developing, agronomists and university experts recommend planting soybeans with different sources of SCN resistance.

“In the past few years, we have seen more cases of nematodes reproducing in fields planted with varieties using the traditional source of resistance (PI 88788) which is deployed in many Midwest varieties,” says Greg Tylka, Iowa State University plant pathologist, specializing in soybean cyst nematode, biology and management research.

“For many years, PI 88788 has been the main source of resistance used to control SCN, but by using this source as a primary control, there have been cases where nematode control has not been as effective,” says Tylka. “While these reports have been isolated, they are increasing in number. Reports of PI 88788 resistance being overcome and signs that SCN continues to spread north have certainly encouraged the development and expansion of SCN-resistant varieties.”

The Peking source has not been widely deployed in the Midwest. However, Pioneer researchers, using sophisticated molecular marker technology, have integrated Peking SCN resistance into a number of high-performance soybean varieties. Marker-assisted selection (MAS) allows Pioneer breeders to track the genes associated with resistance and increases their effectiveness in combining yield with SCN genes. Selecting for resistance markers makes the breeding process both faster and more efficient.

“In addition to the source of resistance, the genetic background also plays a role in a variety’s ability to control SCN,” says Thompson. “Rotating resistant varieties is often a good strategy for controlling an SCN population.”

Determining SCN Levels in the Field
“Growers can experience SCN damage and not realize it - making SCN an extremely difficult challenge to manage,” says Tylka. “There can be as much as 30 percent to 40 percent potential yield loss due to SCN damage below ground, but the plant actually can look healthy above ground. Therefore, growers may attribute yield loss at harvest time to other factors during the growing season.”

Tylka encourages growers to consider either soil sampling or examining root systems to determine if SCN is present. There are several factors to keep in mind for both management tools. Soil sampling is more costly, but can be done nearly anytime of the year, and once a baseline is determined, soil sampling can be spread out to every six to eight years. Examining root systems is virtually a no-cost option, but can be done only at certain times during the growing season - July or August.

“Growers need to know that besides waging a costly battle on its own, SCN also can intensify other yield-reducing diseases for soybeans,” says Tylka. “Research shows SCN can worsen soilborne, fungal diseases such as sudden death syndrome (SDS) and brown stem rot (BSR). Keeping SCN numbers under control also can benefit growers by limiting the impact of other diseases.”

While research has focused mainly on yield loss caused by SCN, now the focus is starting to shift to determine the potential quality damage. According to Tylka, Iowa State University, with soybean check-off funding, is exploring if SCN has an impact on soybean composition, such as oil or protein content. With the ever-increasing production of specialty crops, including low linolenic and high oleic soybeans, retaining desired composition is a key end result.

New SCN Resistance Varieties for 2008
“Maintaining adequate soil fertility, reducing compaction, and controlling weeds, diseases and insects all improve soybean growth and plant health,” says Thompson. “These practices help soybean plants compensate for SCN damage, however, they do not decrease SCN numbers and are not a substitute for practices such as rotating crops and selecting the right SCN-resistant varieties,” adds Thompson.

To help growers address the challenge of SCN, Pioneer is expanding its lineup of soybean varieties with multi-sources of SCN resistance to include products across a wide geographic area in 2008 - including northern and central areas of the Corn Belt.

The following are new Pioneer® brand soybean varieties with SCN resistance:

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90M80 is a Group 0 variety that not only has the Roundup Ready® (RR) gene, but also the Peking source for resistance against SCN, giving Minnesota customers the ability to address the northern movement of SCN.
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91M80 (RR) is a new Group I variety offering excellent performance and solid SDS tolerance in northern areas.
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For early Group II, both 92M11 and 92M21 have the RR gene and the Peking source for SCN. These products will be offered across a large area in 2008 - from Iowa to Minnesota and east to Michigan and Ontario, Canada.
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93M61 (RR) in mid-Group III is a new product for soybean growers looking for SCN resistance in more central Corn Belt areas from Kansas and Nebraska in the West and to Pennsylvania and Maryland in the East and is setting the standard for performance in mid-Group III.

For further information on soybean varieties that help you harvest the greatest profits from your fields, contact your local Pioneer sales professional.