New Soybean Accessions Evaluated for Reaction to Heterodera Glycines Populations.

Soybean Cyst Nematode (SCN, Heterodera glycines Ichinohe) is a serious pest of soybean [Glycine max (L.) Merr.] in the USA and worldwide. Annual yield losses in the USA are estimated to be over $1 billion. These losses have remained stable with the use of resistant cultivars but over time nematodes will adapt to deployed resistance alleles. Currently used resistant cultivars use primarily three or four sources of resistance, and several resistance genes are common among them. Soybean PI88788 and its derived cultivars is the primary source of SCN resistance. It is important to identify new accessions with resistance to SCN as the first step to finding new alleles to provide long- term resistance. We have bioassayed in the greenhouse over 350 newly available accessions from the USDA Soybean Germplasm Collection. We published methods to bioassay including culturing of nematodes to develop near homogeneous populations for stable reactions on soybeans. Several accessions including PIs 567734, 567739A, 567749A, 567762A, 567774A, 606420, 606424, 606430, 606436, 606404, 606443, 612610, 612611, 612612A with resistant reaction were identified, and SCN resistance was confirmed in replicated multiple tests. A female index was calculated using an established method. Female index is the number of nematodes developed on a soybean plant expressed as the percentage of mean number of nematodes on standard susceptible soybean. This was used to determine the reaction of each accession for each nematode population. Data for tests for each nematode population were combined over tests for ANOVA of female indices by the Statistical Analysis System Software,and means were separated with Fisher’s LSD based on Significant F test. We discuss these results.