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, the soybean cyst nematode (SCN), and , causal agent of charcoal rot, are economically important soybean pathogens. Both pathogens are soilborne with spatially aggregated distributions and effects. The objectives of this study were to evaluate the combined effect of and on soybean yield in naturally-infested commercial fields with ordinary least squares and spatial regression models and to evaluate, under environmentally-controlled conditions, the combined effect of and on nematode reHproduction and fungal colonization. Six trials were conducted in fields naturally-infested with and in Ohio. Systematic-grid sampling was used to determine the population densities of and , and soybean yield estimates. Moran's test indicated that the yield from five fields was spatially correlated ( < 0.05) and aggregated. Spatial regression analyses revealed a significant interaction effect between and on soybean yield for fields with high initial population densities of both pathogens. In greenhouse experiments, treatments consisted of alone, alone, and co-infestation of soybean with both pathogens. In these experiments, reproduction was significantly ( < 0.05) reduced in the presence of ; however, soybean tissue fungal colonization was not affected by the presence of . The direct mechanisms by which and interact were not demonstrated in this study. Future studies must be conducted in field and greenhouse to better understand this interaction effect.
PMID: 31535924 [PubMed - as supplied by publisher]