Anaerobic disinfestation induced changes to the soil microbiome, disease incidence and strawberry fruit yields in California field trials

Authors: Mazzola, Mark; MURAMOTO, JOJI - University Of California; SHENNAN, CAROL - University Of California

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2018
Publication Date: 3/15/2018
Citation: Mazzola, M., Muramoto, J., Shennan, C. 2018. Anaerobic disinfestation induced changes to the soil microbiome, disease incidence and strawberry fruit yields in California field trials. Applied Soil Ecology. 127:74-86. https://doi.org/10.1016/j.apsoil.2018.03.009.
DOI: https://doi.org/10.1016/j.apsoil.2018.03.009

Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge for strawberry production in California, and modifications to existing regulations are likely to intensify this challenge by further limiting availability of fumigants on a large percentage of strawberry acreage. Anaerobic soil disinfestation (ASD) was developed in Japan and the Netherlands as an alternative to soil fumigation and involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. Disease control is believed to result from the production certain volatiles that are generated by microorganisms that are active under anaerobic conditions. ASD consistently improved strawberry yields at all three field locations. However, although control of certain strawberry root diseases was observed at each study site, disease control was not uniformly attained across all pathogens present at a given site. ASD treatments increased soil populations of certain potential pathogens, such as Fusarium and Pythium spp., but consistently provided effective suppression of the soilborne pathogen Verticillium dahliae. The level of disease control and strawberry yields that were obtained in response to ASD were dependent on the carbon source used in the ASD process. ASD with rice bran consistently resulted in greater crop yield and control of V. dahliae populations than did ASD conducted using molasses. Effective disease control was associated with changes in overall composition of the soil microbial community that resulted only when a rice bran was utilized as the ASD carbon input. The results from this study demonstrate that informed selection of carbon source to be used in ASD and knowledge of the pathogen population that is present in the strawberry field soil will be essential to successful use of ASD for control of soilborne plant diseases.

Technical Abstract: Soil-borne disease management in California strawberry production systems has historically relied upon pre-plant soil fumigation. Restricted efficacy of currently available fumigant chemistries towards certain pathogens and regulatory actions limiting treated acreage has stimulated interest in development of alternative disease control strategies. Anaerobic soil disinfestation (ASD) demonstrates activity toward an array of soil-borne pathogens, however, there exist limited field-scale trials examining efficacy in strawberry systems. Multiple mechanisms, including the activity of an altered soil microbiome, are reported to function in ASD-induced disease suppression but consistency of the microbial response across soils has not been examined. The present research reports ASD-induced changes in composition of the soil microbiome which occurred in a carbon input-dependent manner and were consistent in two of the three field trials conducted. At all three field sites, ASD treatments that transformed the microbiome were consistently associated with enhanced strawberry yields, but specific compositional attributes of the microbiome in effective treatments were not uniform among all sites. Enhanced yields were associated with control of specific soil-borne pathogens at a given site, however disease control was not uniformly attained across all pathogens resident to a given soil system. Findings demonstrate that informed selection of substrate to be used in ASD and knowledge of the targeted pathogen profile resident to the strawberry field soil will be essential to successful use of ASD in commercial agricultural production settings.