Role of organic acids in the mechanisms of biological soil disinfestation (BSD)

Biological soil disinfestation (BSD), or reductive soil disinfestation, achieved by amendment with organic materials such as wheat bran followed by flooding and covering the soil surface, has been used to control some soilborne diseases including Fusarium wilt and bacterial wilt of tomato. During a BSD treatment, accumulation of acetic acid and/or butyric acid was detected with high-performance liquid chromatography. Survival of Fusarium oxysporum f. sp. lycopersici or Ralstonia solanacearum was suppressed by these organic acids. Amendment of these organic acids into soil suppressed the survival of R. solanacearum at lower concentrations than the maximum detected in BSD treatment, indicating that production of these organic acids is one of the mechanisms of control. However, F. oxysporum f. sp. lycopersici in soil survived with the maximum concentrations of these organic acids achieved by BSD; thus, involvement of factors other than organic acids may be involved.