Shawn P. Conley, Department of Agronomy, University of Wisconsin-Madison, Madison, WI, David A. Marburger, FMC Corporation, Rochelle, IL, Paul David Esker, Universidad de Costa Rica, San Jose, Costa Rica, Ann E MacGuidwin, Plant Pathology, University of Wisconsin - Madison, Madison, WI and Damon L Smith, 1630 Linden Drive, University of Wisconsin-Madison, Madison, WI
Fusarium virguliforme, the causal agent of sudden death syndrome, and Heterodera glycines, soybean cyst nematode (SCN), are economically important pathogens of soybean in Wisconsin. In 2011 and 2012, soil samples submitted from growers throughout the state to a SCN detection program were screened for number of SCN eggs using a sieving/centrifugation method and for number of spores g soil-1 of F. virguliforme using a real-time quantitative polymerase chain reaction (RT-qPCR) protocol. In 2011, 135 soil samples were submitted. H. glycines was detected in 56 samples, while only 10 samples were positive for F. virguliforme. In 2012, there were 64 of 318 samples testing positive for H. glycines and 13 testing positive for F. virguliforme. Kendall’s tau rank correlation coefficient was used to describe the relationship between samples that were positive for H. glycines and/or F. virguliforme. Results indicated a negative association (τ = -0.59, P < 0.01). Additionally, a best-fitting logistic regression model that described the probability of detecting H. glycines in a soil sample based on detecting F. virguliforme confirmed the negative correlation. This result suggests that SCN and F. virguliforme do not rely on each other to colonize fields indicating that fields heavily infested with SCN are not necessarily at greater risk of F. virguliforme colonization.