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Effect of Initial Inoculum Densities of Heterodera glycines on Growth of Soybean and Kidney Bean and Their Efficiency as Hosts Under Greenhouse Conditions. G. S. Abawi, Associate professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456; B. J. Jacobsen, professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 74:1470-1474. Accepted for publication 30 July 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1470.

There was no significant difference (P = 0.05) in the number of second-stage larvae of the soybean cyst nematode (SCN) that penetrated the roots of cultivar California Light Red Kidney bean (CLRK) and the soybean cultivar Amsoy 71, as determined by direct microscopic examination of stained roots or by the shaker technique. Larval development was similar in both crops. Mature males and females were first observed 14 and 18 days after planting, respectively. Oviferous females and brown cysts were detected 21 and 32 days after planting, respectively. The final population (Pf) densities of SCN in soils planted to both crops did not differ significantly. In a 6-wk greenhouse test, the Pf density in soil planted to Amsoy 71 and CLRK was 114 and 121 viable eggs and larvae per cubic centimeter of soil, respectively. There was a close correlation between initial population (Pi) density of the SCN and growth of Amsoy 71 but not of CLRK. In one test, plant dry weight of Amsoy 71 at 6 wk after planting was 0.56, 0.58, 0.56, 0.48, 0.43, and 0.31 g at Pi densities of 0, 3, 6, 12, 24, and 48 viable eggs and larvae of SCN per cubic centimeter of soil, respectively. Dry weight of CLRK at the same Pf densities was 1.47, 1.82, 1.61, 1.65, 1.16, and 1.40 g, respectively. Also, growth and root-rot severity ratings of CLRK were not significantly affected when soil from a bean field with a history of severe Fusarium root rot was infested with SCN at Pi densities from 1 to 100 eggs and larvae per cubic centimeter of soil.