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Population Development, Reproductive Behavior, and Morphology of Race 4 of the Soybean Cyst Nematode, Heterodera glycines, on Resistant Soybeans. G. R. Noel, Research Plant Pathologist, USDA, ARS, and Assistant Professor of Nematology, Department of Plant Pathology, University of Illinois, Urbana 61801. B. A. Stanger and P. V. Bloor, Assistant Plant Pathologists, Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 67:179-182. Accepted for publication 9 June 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-179.

The effects of the soybean lines Toyosuzu, Essex, Cloud, PI 87637-1, Bedford, L77-994, PI 209332, and PI 88788 on numbers of females attaining maturity, reproductive behavior, and morphology of Heterodera glycines race 4 were determined. As the level of resistance increased, fewer females developed, and they were smaller and produced fewer eggs. The number of egg masses produced, egg mass size, and number of eggs per egg mass were also less on resistant lines. Numbers of mature females and reproduction were high on Essex and Toyosuzu and moderate on Cloud. PI 87631-1, PI 89772, and Bedford produced similar low levels of mature females, but less total reproduction occurred on Bedford. The fewest mature females occurred on PI 88788, PI 209332, and L77-994. L77-994 and Bedford both derive their race 4 resistance from PI 88788. The amount of nematode reproduction was similar but the number of females attaining maturity was greater on Bedford than on L77-994. The number of mature females on L77-994 and PI 88788 was similar, but less reproduction occurred on PI 88788 than on L77-994 and Bedford. These differing reactions between PI 88788 and its progeny support the hypothesis of residual effects of defeated resistance genes. Resistance defined on the basis of nematode reproduction is more precise than that based solely on the number of females attaining maturity in a single nematode generation.

Keyword(s): cyst nematodes, Glycine max.