Verification of SCN Resistance in Soybean Varieties
Laura Lindsey and Terry Niblack
Introduction. Over 80% of soybean fields in Ohio have soybean cyst nematode (SCN). Market analysis in the Midwest has shown that most farmers believe that planting a variety labeled "SCN-Resistant" will protect them from yield loss due to SCN. The label "SCN-Resistant" means the variety may be resistant to SCN Type 0 (fomerly known as "race 3"). However, most of the SCN populations in Ohio are SCN Type 2, not 0. Knowing the level of SCN resistance in soybean varieties will enable farmers to make more informed decisions about varieties.
Objective. The study objective was to test soybean varieties for their actual levels of resistance to SCN Type 2 (most common in Ohio) using a published, standard protocol.
Female index. The female index of each soybean variety was measured. The female index is determined in greenhouse assays where the average number of female cysts on a resistant cultivar is divided by the average number of female cysts on a susceptible cultivar and multiplied by 100.
Interpretation of results. A female index <10 is considered resistant, 10-30 is considered moderately resistant, 30-60 is considered moderately susceptible, and >60 is considered susceptible. However, most varieties with a female index rating up to 50 will yield more than varieties with a higher (more susceptible) rating when SCN is present in yield-reducing numbers.
Conclusions. Only one variety (out of 237) in the test was resistant to SCN Type 2. Sixty-eight percent of the varieties had a female index <50 indicating that these varieties would likely yield more than varieties with a higher remale index if SCN was present in yield-reducing numbers.
- This project was funded by the Ohio Soybean Council.