Yield loss in soybean caused by Heterodera glycines

Yields of four soybean cultivars were measured for 4 years in a field infested with Heterodera glycines race 3 and in a field infested with H. glycines race 14. Cultivars included Hutcheson (susceptible to both races), Deltapine 415 (resistant to race 3 and susceptible to race 14), Asgrow 5979 (resistant to both races), and Harwig (resistant to both races as well as most other known races of H. glycines). Although no above-ground symptoms of nematode infection were visible, mean yield was 16-32% greater for Asgrow 5979 than for Hutcheson. Yield for Deltpine 415 was similar to that of Asgrow 5979 in the field infested with race 3 and similar to that of Hutcheson in the race 14-infested field. Hartwig produced lower yields than Asgrow 5979 in both fields. Yield differences, particularly between Asgrow 5979 and Hutcheson, were attributed primarily to nematodes because both cultivars have been shown to produce similar yields in the absence of H. glycines. This study illustrates the importance of knowing which race of the nematode is prevalent in a field and demonstrates that the nematode can cause significant yield loss in the absence of visible symptoms of infection.