A selective medium for rapid detection and quantification of Fusarium oxysporum in soil

Fusarium oxysporum is a soil-borne fungal pathogen that can survive in the soil for a long time, and penetrates alfalfa (Medicago sativa) through roots to cause disease, seriously affecting the yield and quality of alfalfa. This study developed a selective medium that can fast and efficiently isolate this pathogen in order to specifically isolate F. oxysporum in soil, and this medium can isolate this pathogen in the bulk soil of diseased plants. The isolated strains were identified as F. oxysporum based on morphology as well as ITS and TEF double-loci sequences, and the mean isolation rate of this pathogen reached 79.3% in soils with different spore concentration of this pathogen. The colonies of F. oxysporum were white and round with dense mycelia at the early stage of growth on this medium; at the later stage, the mycelia were loose and fluffy, with jagged notches on the edge of the colony and light yellow in the center of the colony. The selective isolation medium in this study can quickly and efficiently detect and quantify F. oxysporum in soil, which provides a basis for studying the occurrence as well monitoring and early warning of soil-borne diseases in alfalfa.