Soybean genotypes are evaluated for resistance to soybean cyst nematode (SCN), Heterodera glycines, by growing the plants in infested soil-sand mix for approximately 30 days, after which the numbers of adult SCN females and cysts on the roots is assessed. Alternatively, non-infested soil-sand mix may be infested with an SCN egg suspension.
The reaction of individual plants of each soybean genotype to SCN is then classified based on the criteria presented by D.P. Schmitt and G. Shannon in Differentiating Soybean Responses to Heterodera glycines races, Crop Science 32(1):275-277 (1992).
Procedure
Two or three seeds of each soybean genotype to be evaluated are planted directly into individual replicate cone-tainers filled with soil-sand mix infested with Race 3 SCN/HG Type 0 (or selected other SCN populations if desired and available); a minimum of five replicates per genotype is recommended.
Additionally, three seeds of Lee, PI548402 (Peking), PI88788, PI90763, PI437654, PI209332, PI89772, PI548316, PI438489B, and Pickett (the HG Type and race differential genotypes) are planted into separate replicate cone-tainers filled with the same SCN-infested soil-sand mix.
All cone-tainers are placed in an arbitrarily-determined position in a greenhouse waterbath and incubated at constant 27°C temperatures under natural lighting conditions. The cone-tainers are observed every day, and the second and third seedlings that emerge within each cone-tainer are removed and only the first seedling that emerges in each cone-tainer is used in the evaluation.
After about 30 days, the number of females and cysts on each soybean root is determined by direct visual observation, and each replicate plant of each genotype is classified into categories based on the number of females and cysts formed on the genotypes relative to the number formed on Lee or Lee74, which are considered by most soybean breeders to be universal SCN-susceptible soybean genotypes. An HG Type/Race test is conducted to confirm the HG Type/Race of SCN population used in the screen.
The unused seed of the soybean genotypes is returned to the client with the report of the results, or if preferred, the seed will be destroyed at the end of the experiment.