Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: September 14, 2012
Publication Date: N/A
Interpretive Summary: Anaerobic soil disinfestation (ASD), also referred to as biological soil disinfestation, is an effective alternative to chemical fumigants for controlling soilborne pathogens. ASD is a novel approach for controlling a broad-spectrum of plant pathogens while being environmentally safe. The fundamental aspect of ASD consists of creating an environment which is conducive for facultative and obligate anaerobes to grow. Previous research has indicated that secondary metabolites generated by facultative anaerobic and obligate anaerobic bacterial communities found commonly in soil are one of the factors that aids in controlling soilborne pathogens. Yet, currently it is unknown which soil microbe populations are essential for ASD. Using molecular techniques applied to soil from two field trials, a bacterial population shift between pretreatment and post-treated soil has been detected. Three bacterial species of interest have been identified. A correlation has been observed between the lowering of the soil pH and the increase of these populations over time.
Technical Abstract: Previous research has shown that application of anaerobic soil disinfestation (ASD) controls soilborne plant pathogens as effectively as methyl bromide (MeBr) fumigation. Vegetable yields from ASD-treated fields were comparable or exceeded those from fields treated with MeBr in two field trials. The combination of a lack of oxygen and an increase in temperature contribute to pathogen control, however the major component of ASD is the secondary metabolites produced by anaerobic bacteria. However, which bacteria are essential for ASD remains unknown. The goal of this study was to determine the bacterial species important for generating anaerobicity in the field. Soil samples were taken from two different fields treated with ASD. The pH of one of the ASD fields was taken every 2-3 days and the pH level dropped as low as 4.33, while the untreated control remained at 6.20. The decrease of pH correlated with the increase of various bacterial populations. Using length heterogeneity pcr (LH-pcr) it was observed that bacterial populations shifted upon comparing pretreated and post-treated samples. In the post-treatment samples, three different bacterial species dominated the community by as much as 67% of the total population. However upon comparing these species to the pretreated samples they account for less than 16% of the total population. One of these species was not detected in the pretreatment samples. Further analysis should reveal the identity of the species associated with this population shift and potentially, the resulting oxygen-depletion.