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Poster: Epidemiology: Risk Assessment


Evaluating soybean production in fields infested with Heterodera glycines and Macrophomina phaseolina with spatial regression analyses
H. LOPEZ-NICORA (1), J. Carr (1), A. Dorrance (2), T. Niblack (1) (1) The Ohio State University, U.S.A.; (2) The Ohio State University, U.S.A.

Heterodera glycines, the soybean cyst nematode, and Macrophomina phaseolina, causal agent of charcoal rot, are economically important soybean pathogens. The spatial distribution of both pathogens was previously described as aggregated. The objective of this study was to use and compare ordinary least squares (OLS) and spatial regression models to evaluate soybean production in fields co-infested with these pathogens and to assess their role in soybean performance. Six trials were conducted in fields naturally infested with H. glycines and M. phaseolina. Within 30 days after planting, a 10×10 grid of contiguous quadrats (7.62×7.62 m) was marked in each field. Fifteen to 20 soil cores were collected at each grid for initial (Pi) and final (Pf) H. glycines egg and M. phaseolina colony-forming unit (CFU) counts, respectively. Twenty-five plants were collected and hand-threshed from every grid for yield analysis. Moran’s I test indicated that yields from five fields were spatially correlated (P < 0.05). In these fields, spatial error and spatial lag regression models were fitted and compared with the OLS model, which does not account for spatial correlation. Spatial regression analyses revealed a significant interaction effect between H. glycines and M. phaseolina on soybean yield for fields with high initial Pi of both pathogens. Results from this study will aid in long-term disease management and evaluation of pathogen interaction in reducing crop production.