Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2006
Publication Date: June 1, 2006
Citation: Donald, P.A., Young, L.D. 2006. Resistance identification for soybean cyst nematode: a comparison of rating method and inoculum levels.. Journal of Nematology. Vol 38:217. Technical Abstract: Soybean cyst nematode resistance in soybean germplasm is an important tool for management of the nematode. However, evaluation methods to identify resistance have not been standardized. Two techniques were compared to evaluate plant resistance using races 3 and 14 under greenhouse test using an inoculum level of 1,000 eggs/mL . A visual rating (VR) with five numeric categories was compared to microscopic enumeration of cysts on the roots and computation of a female index (FI) which has been suggested for use in four resistance categories. The study consisted of 673 entries from the Tennessee State Soybean Variety Test over three years. The VR had larger F values and lower coefficient of variation than the FI. There is a significant increase in the amount of time required to collect data for the FI compared to the VR however environmental conditions can greatly affect visualization of cysts in the VR method. Two inoculum levels, 1,000 and 4,000 eggs/mL, were tested with both races on the seven indicator lines plus susceptible check for the HG Type Test. No significant differences were seen in the FI at the two inoculum levels for race 3. The race 14 standard deviation FI was higher at the lower inoculum level than the higher inoculum level and there were significant differences between indicator lines at the higher inoculum level. The VR system is a less time consuming procedure than the FI in identifying resistance to soybean cyst nematode. Inoculum level can affect identification of resistant soybean lines in certain races.