During August 2003, soybean (Glycine max) plants from Richland County, North Dakota with white-to-yellow, lemon-shaped structures on the roots were brought to the North Dakota State University Plant Diagnostic Laboratory. To confirm that the structures were females of a cyst nematode, they were crushed and observed microscopically to determine if nematode eggs and second-stage juveniles were present. Morphology of the second-stage juveniles was consistent with Heterodera glycines, the soybean cyst nematode (SCN). A survey was conducted in soybean fields in 34 km2 around the field in which the samples originated. Ten of twenty fields surveyed had visible females on the roots of plants. Symptoms observed in those fields included patches of stunted, chlorotic, and dead plants. Soil samples were collected from selected areas within eight fields, eggs were extracted using standard soil sieving techniques, and egg numbers were determined. Egg numbers ranged from 550 to 20,000 eggs per 100 cm3 of soil. SCN collected from two different fields, designated as Dwight and LaMars, were used to determine their HG Type. Standardized procedures (1) were used in a growth chamber set at 27°C with 16-h days. Pots in the test were organized in a completely randomized design with three replicates; the test was repeated over time. After 30 days, females were extracted from roots and counted, and a female index (FI) was calculated for each indicator line (1). The mean number of females on susceptible standard cv. Lee 74, was 110. The Dwight SCN population had an FI of 5.3 on plant introduction (PI) 88788, 1.5 on PI 209332, 5.8 on PI 548316 (Cloud), and 0 on all other indicator lines. The LaMars population had an FI of 1.0 on PI 88788, 3.1 on PI 548316 (Cloud), and 0 on all other indicator lines. These results indicate that both SCN populations tested are HG Type 0. To our knowledge, this is the first report of SCN on soybean in North Dakota. Because other hosts of SCN, as well as soybean, are economically important in North Dakota, such as dry edible bean (Phaseolus vulgaris) and dry pea (Pisum sativum), this disease could adversely impact several commodities throughout the state.
Reference: (1) T. L. Niblack et al. J. Nematol. 34:279, 2002.