Effects of Continuous Culture of Resistant Soybean Cultivars on Soybean Cyst Nematode Reproduction. L. D. Young, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, West Tennessee Experiment Station, Jackson 38301. Plant Dis. 68:237-239. Accepted for publication 13 September 1983. 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, 1984. DOI: 10.1094/PD-68-237.

Soybean cyst nematode (SCN) populations were evaluated from 17 commercial fields in which a cultivar resistant to SCN races 3 and 4 had been grown continuously for 3–6 yr. Index of parasitism (IP, number of cysts on a soybean line relative to 100 on Essex) values for SCN reproduction ranging from 38 to 70 were obtained when the resistant cultivar Bedford was grown in infested soil for 30 days. Seed yields of resistant cultivars grown in these fields have not declined measurably. These results may be compared with those from an earlier study in which Bedford, grown for the first time in soil infested with SCN race 4, had an IP value of 32 when compared with three susceptible cultivars but gave no yield response from application of nematicides. Significantly less reproduction occurred on soybean strains J74-88, PI 89772, and PI 90763 than on Bedford; reproduction on Peking, D72-8927, PI 88788, and PI 209332 was intermediate and varied among SCN populations. Reproduction of these SCN populations on the soybean strains was similar to that obtained from recent greenhouse selection experiments involving the soybeans grown in SCN race 4 soil.

Keyword(s): races, resistance.