Soybean cyst nematode (SCN) is the most devastating and yield limiting pest of soybean in the United States. The nematodes attack and destroy soybean roots resulting in over one billion dollars in crop losses each year. There are several different varieties or races of the nematodes making it more difficult to find resistant varieties. A soybean variety might be resistant to one variety, but not another. Our laboratory is conducting research to find soybean varieties that are resistant to several or all of the nematode races.

Our highly inbred nematode populations are labeled by race number. We have six races that we routinely use for phenotyping.

With each experiment we conduct, several lines are included as controls. They are used to confirm the race of nematodes applied to the study. Pickett, Hutcheson, and Lee 74 are also included in the differential set.

Greenhouse Protocol

1. Seeds are germinated in sterile germination pouches for approximately 3 – 4 days at room temperature.
2. Seedlings are transplanted to micropots containing 100 cc's of sterilized sandy silt loam soil and labeled with barcodes.
3. Inoculation of seedlings with 2,000 nematode eggs per plant occurs approximately 3 days after transplanting.
4. Plants are grown for 30 days under greenhouse lighting. Pots are suspended in temperature controlled waterbaths to maintain soil temperature near 27°C.
5. At harvest, the plant tops are cut off and the soil is soaked off the roots. Roots are placed in sample vials and transported to the laboratory for analysis. (see Lab Protocol).

Laboratory Protocol

1. Sample vials from the greenhouse are stored in cold storage after harvest.
2. For analysis, cysts are washed from each root and scanned in petri dishes on the Carestream 4000MM Pro Image Station and an image of the dish is taken using a fluorescent light wavelength to cause the nematode cysts to fluoresce.
3. The image station software automatically counts the number of cysts per dish using fluorescence and size/shape parameters.
4. Each picture is reviewed for accuracy and then stored on an external hard drive..
5. Cyst counts for each line are averaged across reps within each race and then the female index (FI) is calculated using the average of the susceptible control Hutcheson in the following equation: FI = avg #cysts (line) ÷ avg #cysts ( control) *100.