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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Research Project #439004

Research Project: Develop a Microencapsulation Platform for Xanthomonas Campestris that Supports Bacterial Survival and Disease

Location: Foreign Disease-Weed Science Research

Project Number: 8044-22000-047-003-A
Project Type: Cooperative Agreement

Start Date: Sep 1, 2020
End Date: Aug 31, 2021

The purpose of our proposed research is to investigate and develop value-added synthetic encapsulation matrices for microbial biopesticides of invasive weeds. We propose a moisture-responsive platform to protect beneficial bacteria against harsh environmental conditions such as humidity and temperature; moreover, the proposed approach enhances the targeted attachment of bacteria, increases the rate of weed infection, and sustains bacterial release on the weed’s phyllosphere. Encapsulation is a promising, innovative technology that can be used to protect and sustain the release of diverse cargos under specific environmental conditions. While traditionally considered for applications such as drug-delivery, encapsulation platforms can also be employed to load a variety of microorganisms as cargo and engineered for diverse pathosystems. We will study the phytopathogenic bacteria, X. campestris strain 18048, for the invasive weed of interest, garlic mustard, to increase the efficacy of infection, dispersal, survival, and the sustained release of X. campestris in both lab-scale and field studies (greenhouse).

The garlic mustard bacterial pathogen, X. campestris strain 18048, will be encapsulated with supplemented promoting agents such as inulin or oligosaccharides and xanthan gum for stabilization. We propose two strategies for the microencapsulation of X. campestris that will aid in (i) leaf attachment and (ii) destructive impact (i.e., plant wounding). In the first strategy, X. campestris will be mixed with negatively charged gum such as xanthan gum at different concentrations, as xanthan acts as a natural X. campestris stabilizer. This mixture will then be added to a positively charged polysaccharide such as chitosan solution to form a microparticle shell with electrostatic interactions between xanthan and chitosan using a coacervation technique. In order to achieve stable microcapsules, we will use cross-linkers such as sodium tripolyphosphate for strengthening the chitosan shell. For the second strategy, we have the same microcapsules as the first strategy except silica-based layered double hydroxide (LDH) nanosheets will be added to the microcapsules to enhance moisture retention and increase the bacterial survival rates as well as wounding the leaves. We also hypothesize that the LDH will attach to the leaf surface for a longer duration and introduce micro-abrasions to aid in bacterial penetration. Our first strategy gives us the option of increased adhesiveness to the leaf surface and bacterial protection, while the second strategy gives both features and, in addition, the option to cause micro-abrasive wounds on the leaf surface for increased rates of bacterial penetration and disease development.