Document Type

Thesis - University Access Only

Award Date

1997

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

A 1995 survey resulted in the first report of soybean cyst nematode (SCN), Heterodera glycines Ichinohe in South Dakota. Soil cores were collected from 255 fields in 12 eastern South Dakota counties. Soybean cyst nematode populations were detected in 11 fields in Union county. A 1996 survey consisting of 256 fields in 11 counties detected an additional three fields in Union county and 20 fields in Turner County infested with SCN. Turner County was measured on the race differentials in greenhouse studies. Both isolates were identified as race 3. A separate race test indicated that culturing a race 3 isolate on the resistant cultivar Bell in the greenhouse for three months did not cause a race shift. Greenhouse assessments indicated that the South Dakota State University experimental soybean cultivars SD94-495, SD93-490, SD95-696, SD93-522, SD93-522 (early and late), SD95- 710, SD95-698, SD95-717, SD95-722, SD95-726, SD95-689, and SD95-724 were resistant to SCN. Host range studies indicated that three native legumes (strawberry tick clover, Canada tick clover, and hairy vetch), five cultivated legumes (string bean, navy bean, tendergreen bean, lima bean, and little marvel pea), and tomato var. Rutgers as hosts of a South Dakota isolate of SCN. This is the first study to report Canada tick clover as a host for SCN. A pathogenicity study indicated the number of cysts produced on the resistant cultivar Bell and susceptible cultivar Hardin generally increased as inoculum levels increased. Numbers of cysts produced on Bell were lower or cysts were smaller than those produced on Hardin at all inoculum levels. Average top weights of Hardin inoculated with various levels of SCN were significantly lower than the control. Field test plots planted to the resistant cultivar Bell and susceptible cultivar Hardin were sampled bi-weekly and populations were recorded to determine population dynamics over the growing season. Results indicated a reduction in SCN populations in those plots planted to Bell, while those planted with Hardin generally increased over the growing season. Populations of SCN in five surrounding corn fields planted to soybeans the prior year decreased over the 1996 growing season. Resistant soybean cultivars in the small plot test and in field length test strips yielded higher and generally had higher yield components than susceptible soybean cultivars. Soybean cyst nematode populations in the small plot test planted to resistant soybean cultivars generally decreased from planting date to harvest date while populations in plots planted to susceptible soybean cultivars generally increased. Field evaluations of resistant and susceptible cultivars indicated that yields of susceptible cultivars are reduced up to 48%. Thus, SCN must be regarded as a significant threat to South Dakota soybean production.

Library of Congress Subject Headings

Soybean cyst nematode -- South Dakota

Soybean -- Disease and pest resistance -- South Dakota

Format

application/pdf

Number of Pages

88

Publisher

South Dakota State University

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