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Determining Heterodera glycines HG Types to Improve Soybean Cyst Nematode Management in South Dakota
E. Byamukama (1), K. ACHARYA (1), G. L. Tylka (2). (1) South Dakota State University, Brookings, SD, U.S.A.; (2) Iowa State University, Ames, IA, U.S.A.

Soybean cyst nematode (SCN; <i>Heterodera glycines</i>) is the most important yield-limiting factor of soybean in the United States. In South Dakota, SCN has been found in 29 counties so far and continues to spread. Determining the HG type of the SCN populations reveals the diversity of the SCN populations and the sources of resistance that would be most effective for management. To determine the HG types prevalent in South Dakota, 220 soil samples were collected from 7 to 8 arbitrarily selected fields in each of the 28 counties. SCN was detected in 69 (31%) fields, and combined egg and juvenile counts ranged from 50 to 65,200 per 100 cm<sup>3</sup> of soil. The SCN population in each soil sample was grown on the seven SCN HG type test indicator soybean lines and William 82 as a susceptible check. A female index (FI) was calculated based on the number of females found on each differential line relative to the susceptible check. Female indices equal to or greater than 10% in any line was assigned as that HG type. Out of 50 SCN populations on which HG type tests were done, 66% had FI ≥10% on Cloud, 30% on PI88788, 24% on PI 209332, 4% on Peking, 4% on PI 90736, and 4% on PI89722. None of the SCN populations had FI ≥10% on PI 437654. HG types with >10% reproduction on indicator lines 2, 5 and 7 were most prevalent in these samples, and use of these sources of resistance should be integrated with nonhost crops and SCN-resistant cultivars should be rotated for sustainable SCN management.

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