2012 Annual Report
1a.Objectives (from AD-416):
The objective of this program is to identify and implement an integrated management non-fumigant methodology to control soilborne pathogens and weeds in strawberry production systems. The effects of anaerobic soil disinfestation, mustard seed meal amendments and organic acid material alone or in combination on fruit yield, soilborne disease and weed control will be determined. The contribution from this unit will focus assessing efficacy of these treatments, determining the role of soil biology in any observed disease control, and identifying the functional biological elements that have a role in disease suppression.
1b.Approach (from AD-416):
The capacity of different control strategies and integrated methods for suppression strawberry root infection will be determined in large field assays and in greenhouse assays. Greenhouse trials will focus on the biological ramifications of such control methods on soil biology, the temporal nature of these changes, and the effect of these changes on disease control. Based upon the findings from these experiments field trials may be modified and integration strategies altered to enhance control efficacy.
This project relates to objective 1 of the associated in-house project, which seeks to determine the relative contribution of chemistry and soil biology to the control of soilborne plant diseases that is realized though soil incorporation of various organic material including brassicaceae seed meals. The effect of soil treatments on soil microbial community composition and incidence of root infection by specific pathogens was determined using molecular and culture-based methods. Based upon a molecular analysis of microbial community profiles, treatment-specific effects on fungal and bacterial community composition were identified. Genetic analysis of microbial community composition demonstrated that anaerobic soil disinfestation (ASD) had an over-riding and dominant influence on the eventual structure of the fungal and bacterial communities. Irrespective of treatment combinations, all plots containing ASD as a component of the soil treatment, such as ASD + organic acids or ASD + mustard seed meal, possessed microbial community profiles that were more similar to each other than the control or fumigation treatments. Likewise, soil microbial communities from treatments possessing a mustard meal component were genetically similar, and were more similar to the ASD treatment than the control and fumigation treatments. Interestingly, the microbial community from steam treated and control soils formed a cluster of genetic similarity. The potential role of soil microbiology in disease control attained in response to ASD was evaluated in preliminary studies using Pythium ultimum as the test pathogen. ASD effectively controlled this pathogen in both a natural soil and a pasteurized soil system suggesting that soil biology may not have a dominant functional role in initial disease control. The capacity of the ASD treatment to provide long-term suppressiveness of soil to root infection by P. ultimum was also evaluated. In this system, the natural ASD treated soil was suppressive to root infection by an introduced isolate of P. ultimum, however suppressiveness was abolished when ASD treated soils were pasteurized prior to pathogen infestation. This finding demonstrates that ASD can induce long-term control of soil-borne pathogens, and that soil biology has an instrumental role in the induction of this disease suppression.