Toxic organic acids produced in biological soil disinfestation mainly caused the suppression of Fusarium oxysporum f. sp. cubense

Abstract

Biological soil disinfestation (BSD) is an effective and environmentally friendly way to suppress soil-borne pathogens. Although it is increasingly used in USA, the Netherlands and Japan, its precise mechanism has not been well quantified so far. Quantitative real-time PCR, denaturing gradient gel electrophoresis and high performance liquid chromatography were used for investigating the role of organic acids in the mechanisms of BSD. The results showed that BSD significantly reduced the population of Fusarium oxysporum in soil. Simultaneously, in BSD treatments, the soil pH significantly decreased and some organic acid producers, such as Clostridia sp., were observed. Four kinds of toxic organic acids to F. oxysporum were detected in soil solutions of BSD treatments. Acetic acid and butyric acid were the primary organic acids, followed by small amounts of isovaleric acid and propionic acid. The verification test directly demonstrated that the toxic organic acids with the maximal doses detected in BSD significantly suppressed F. oxysporum, Rhizoctonia solani and Ralstonia solanacearum.