Abstract
Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a major pest of soybean, Glycine max L. Merr. Several plant introductions resistant to Race 3 have been identified, however the genetic relationships for resistance among them are not known. The F2 plants and F3 families from seven different crosses involving resistant parents were evaluated in the greenhouse to determine if the genes for resistance were identical or different from the genes in ‘Peking’ and/or PI 90763. Each seedling was inoculated with 1000 eggs and juveniles of SCN Race 3. Plant roots were washed after 30 d and white females enumerated. Based on the index of parasitism (IP) F2 plants and F3 families were categorized into resistant, segregating, or susceptible. The Chi‐square test was applied to determine goodness of fit between the observed and expected genetic ratios. Peking was found to have genes in common with PI 90763 and PI 438489B; whereas PI 90763 has genes in common with PI 438489BP, PI 404166, and PI 404198A. The cross between Peking and PI 88788 indicated segregation for one dominant and one recessive gene, and segregation in the cross PI 88788 × PI 438496B suggested two independent dominant genes. This information will assist soybean breeders in choosing additional resistant sources to SCN Race 3 in commercial cultivar development, thus providing a broader genetic base.
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