Submitted to: Controlled Release Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/2/2012
Publication Date: 7/10/2012
Citation: Kim, I., Pusey, P.L., Zhao, Y., Korban, S.S., Choi, H., Kim, K. 2012. Controlled release of Pantoea agglomerans E325 for biocontrol of fire blight. Controlled Release Journal. 161:109-115. Interpretive Summary: Fire blight is a destructive bacterial disease of apple and pear that is initiated in flowers. Control with antibiotics has become less effective due to the development of resistance in the causal organism (Erwinia amylovora). An alternative approach is to use beneficial microorganisms that preemptively colonize floral surfaces and prevent E. amylovora from becoming established. The commercially available biocontrol agent, Pantoea agglomerans strain E325, first discovered by ARS scientists, significantly reduces fire blight but possibly could be enhanced through delivery in microcapsules made of a natural substance from algae (alginate) that increases its survival and multiplication, and controls its release. When microencapsulation of E325 was evaluated on floral surfaces in the laboratory, results were promising and provided a foundation for further investigation. It is hoped that this technology will improve the establishment of biocontrol agents in plant environments and specifically lead to more effective control of the fire blight disease.
Technical Abstract: Microencapsulation and controlled release of Pantoea agglomerans strain E325 (E325), which is an antagonist to bacterial pathogen (Erwinia amylovora) of fire blight, a devastating disease of apple and pear, have been investigated. Uniform core-shell alginate microcapsules (AMCs), 60-300 µm in diameter, were fabricated to encapsulate E325 in the core, along with nutrients, to preserve viability and promote proliferation. Controlled release of E325 was achieved by separately adjusting alginate concentrations in the shell and core solutions, and by modifying sizes of AMCs. Viability of E325 was monitored via fluorescent staining indicating either lack of or minimal stress during or after encapsulation. Release of E325 was measured for various encapsulation conditions over the period of flower conduciveness to pathogen colonization. Proliferation of E325 within AMCs, followed by their subsequent release therefrom and colonization activities within confines of apple flowers were studied using rfp-labeled E325. Highly promising results were obtained, providing 'proof of concept' and foundation for further studies on development of an effective plant disease management strategy employing bacterial antagonists as biocontrol agents.