Effect of Heterodera glycines on Charcoal Rot Severity in Soybean Cultivars Resistant and Susceptible to Soybean Cyst Nematode.

Field experiments were conducted in two soil types in northeastern Kansas to evaluate the influence of Heterodera glycines on the severity of charcoal rot in group III soybean cultivars resistant and susceptible to soybean cyst nematode race 3. Resistant cultivars Asgrow 3307 and Fayette and susceptible cultivars Asgrow 3127, Harper, Pella, Sprite, and Williams 82 were planted in carbofuran-treated and nontreated plots. Heterodera glycines and the charcoal rot fungus, Macrophomina phaseolina, were suppressed by carbofuran treatment in loamy sand, but not loam soil, and by nematode-resistant cultivars in both soils. Root densities of the fungus were positively correlated with nematode densities and negatively correlated with seed yield at both locations. Results indicate that H. glycines infection can increase colonization of soybean roots by M. phaseolina which may increase losses due to charcoal rot.