Assessment of Commercial Soybean Cultivars for Resistance Against Prevalent Heterodera glycines Populations of South Dakota

Abstract

Soybean cyst nematode (SCN; Heterodera glycines) is the most important yield limiting factor of soybean production in South Dakota and the main management practice is planting SCN-resistant cultivars. The effectiveness of host resistance is often limited by the diversity of SCN populations that can reproduce on resistant varieties. A greenhouse study was set up to determine the response of SCN-resistant commercial soybean cultivars with PI 88788 as the source of SCN resistance genes to the three commonly found SCN H. glycines (HG) types in South Dakota. To screen the soybean cultivars, 3,000 SCN eggs and juveniles of the prevalent HG types 0, 2.5.7, and 7 were each inoculated to 34 commercial soybean cultivars and also a susceptible cultivar, Williams 82, as the control. The female index (FI) was calculated based on the average number of females (cysts) found on each cultivar relative to the susceptible check after 35 days. Cultivars showed a varied response to HG types with all 34 cultivars showing resistance or moderate resistance to HG 0. Less than 9% of the cultivars tested had resistance response and between 82 to 88% had moderate resistance response to both HG 7 and 2.5.7 types. Only one cultivar was rated as susceptible to both HG 7 and 2.5.7. These results indicate that host resistance is still effective in managing SCN in South Dakota. However, use of these cultivars should be combined with crop rotation and rotation within soybean cultivars derived from different resistance sources for sustainable SCN management.