An Efficiently Selective Medium with Dodine for Quantitative Isolation of Metarhizium anisolpliae in Soil

This paper is to determine an efficiently selective medium and its efficiency for quantitative evaluation of the fungus Metarhizium anisopliae as a biocontrol agent applied in soil. The selectivity and detection rate of dodine was investigated at different concentrations. The results showed that 50-200 mg/L of dodine in medium could effectively inhibit non-target fungi in soil and highlight M. anisopliae, while preventing bacterial growth by chloromycetin. But lower dodine concentration, 25 mg/L, could not completely preclude non-target fungi with residues accounted for about 50% of the total colonies. When increasing dodine concentration, M. anisopliae would slow growth, yellow conidiation and decrease colonies. At 50 mg/L of dodine, detection rates get to 69.20% and 71.43% after inoculation of M. anisopliae conidia for 4 d and 6 d. The values were significantly higher than 45.45% and 61.24% detected on 200 mg/L concentration, though significantly lower than 95.56% and 94.72% detected on control medium without dodine in the same inoculation and incubation. Finally, a favorable medium including basic nutrition supplemented with 50 mg/L dodine as selective agent was determined, which can effectively inhibit non-target fungi and extract stably M. anisopliae in 70% efficiency. Inhibition and selection efficiency of selective agent should not be ignored in quantitative detection of microorganism in soil. Properly quantitative assessment of M. anisopliae in field is a necessary foundation for analysis of population dynamics, ecological effects and sustained biocontrol.