Integrated biological and chemical control of soybean root disease caused by Fusarium ipomoeae

Soybean ( Glycine max ) is a globally important crop, but its production is continually threatened by soilborne diseases, particularly those caused by diverse Fusarium species. These pathogens comprise multiple Fusarium species complexes associated with diseases such as damping-off and Fusarium root rot, including the Fusarium incarnatum–equiseti species complex (FIESC). Fusarium ipomoeae , a recently reported soybean-associated species within the FIESC and a primary focus of this study, has been identified as pathogenic to soybean. However, information regarding effective management strategies for this species remains limited. Moreover, the taxonomic complexity of Fusarium species and the lack of integrated management approaches and reliable diagnostic tools continue to constrain the control of Fusarium -induced diseases, particularly those caused by emerging or less-studied species. Thirty-eight Fusarium isolates representing five species complexes, the Fusarium fujikuroi , F. solani , F. nisikadoi , F. incarnatum–equiseti , and F. oxysporum species complexes, were recovered from soybean fields in Korea and identified by molecular phylogenetic analysis. Representative isolates were selected to provide broad phylogenetic coverage across the identified species complexes and clades and were subsequently evaluated for pathogenicity. Among them, Fusarium ipomoeae CMML23-33, identified within the F. incarnatum–equiseti species complex, caused the most severe disease on soybean. Pot assays demonstrated that Pseudomonas brassicacearum CMML23-51 provided the greatest disease suppression (49.5% control efficacy). Among the succinate dehydrogenase inhibitor (SDHI) fungicides, fluopyram (5 mg L −1 ) and pydiflumetofen (4.59 mg L −1 ) achieved the highest efficacy as single treatments (83.3% and 76.1%, respectively), whereas the combined application of P. brassicacearum CMML23-51 with 2.29 mg L −1 pydiflumetofen achieved the highest overall control efficacy (89.5%). A species-specific TaqMan qPCR assay targeting the translation elongation factor 1-alpha gene was developed for sensitive quantification of F. ipomoeae . Quantities of F. ipomoeae DNA detected in pot soils were inversely related to disease suppression. This study provides foundational biological, chemical, and molecular diagnostic components that may contribute to integrated disease management strategies for soybean Fusarium root disease.