Plant & Nematode Screening Services

[ know your SCN Population ]

  POPULATION TYPING  

What is HG type and why it matters
Although a bag of soybean seed may be labeled as SCN-resistant, it does not mean that it will be effective against the population of SCN in your field. "HG" stands for the scientific name for SCN, Heterodera glycines. The HG-type test provides a description of an SCN population that is based on its reproduction on a set of soybean indicator lines that have served as sources of resistance.

BREAK DOWN OF RESISTANCE

The effectiveness of resistance is reduced by continuous cropping of soybean varieties with SCN resistance derived from the same genetic source. This practice decreases the durability of current sources of resistance by selecting for nematode populations that increase well on resistant soybean lines. More than 95% of the market share in the north central USA is dominated by PI 88788-type resistance; the remaining cultivars derive resistance from Peking, PI 437654, or combinations thereof. This has led to the adaptation of SCN to these sources.


STRATEGIC MANAGEMENT

In order to maintain the durability of existing sources of resistance for effective long-term management of SCN, an integrated approach that incorporates crop rotation and regular monitoring of SCN field populations by farmers is absolutely necessary. The HG type test helps farmers strategically select the most effective source of resistance for SCN management in their field.

SAMPLING INSTRUCTIONS FOR HG TYPE TEST

Soil samples for an HG type test should be collected according to guidelines for soil sampling for an SCN egg count. However, at least 40,000 eggs are needed to set-up the HG test. Therefore, a one gallon-sized soil sample should be sent to the laboratory. If an insufficient number of SCN eggs is present in the submitted sample, the SCN population will be increased on a susceptible soybean host in the greenhouse for one month to generate enough eggs for the test. For soil submitted November through April, this step is required to ensure a uniform, meaningful HG test. Soil submitted should be from fields where SCN-resistant soybeans have been grown, the SCN egg counts are increasing, and the field is highly infested. Our HG type test includes the indicator lines Pickett, Peking, PI 88788, PI 90763, and PI 437654. Results are reported as both HG type and race.

CARE OF SOIL SAMPLES

Proper collection and care of samples is extremely important.

Take samples when soil is moist. Put samples in plastic bags, with the label on the outside. Do not let samples dry out!

Nematodes are sensitive to heat. Keep samples in a cool, dark place until they can be mailed. Do not leave samples in the sun or other areas of high temperature.

PACKAGING AND MAILING

  1. Fill out the sample submission form as completely as possible.
  2. Label the sample bags with the submitter's name and sample ID designation given on the sample submission form.
  3. Place sample and submission form in a cardboard mailing box.
  4. Mail samples to SCN Diagnostics:

    SCN Diagnostics
    1721 East Campus Loop
    University of Missouri
    Columbia, MO 65211-5315

For any questions, please call 573-884-9118 or send an email to scndiagnostics@missouri.edu.

For sample volumes greater than 10, please us the population typing request form population typing request form to receive a detailed quote and estimated turn around time.

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