Interactions Between Delia platura and Erwinia amylovora Associated with Insect-Mediated Transmission of Shoot Blight

Abstract

Erwinia amylovora is a bacterial pathogen of rosaceous plants that can be devastating to commercial apple and pear production worldwide. Exopolysaccharide (EPS) production is essential for pathogenicity, aiding in biofilm production, and plant defense protection. EPS also plays an epidemiological role in the form of bacterial ooze, which is generated when E. amylovora builds to such high levels within the parenchyma that it ruptures the plant epidermis and a mixture of bacteria encased in EPS exudes from the injury. Insects such as Delia platura feed on the ooze and become potential vectors in the process. The goal of this study was to investigate interactions between D. platura and E. amylovora to better understand how insects facilitate shoot blight. We demonstrate for the first time that D. platura can successfully transmit pathogen cells that initiate new infections in mechanically damaged apple shoots and that EPS aids in adherence of E. amylovora to the insect surface. We show that flies can carry the bacteria externally for at least 5 days and that they shed a constant daily rate. We also show that E. amylovora strains differing in virulence do not behave differently when associated with D. platura and that consumption of E. amylovora has no effect on insect survival. Our data demonstrate that flies can be efficient facilitators of new shoot blight infections, but the field conditions that make this type of transmission possible require further investigation.[Graphic: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Keywords

• Diptera
• Hemiptera
• Hymenoptera
• Erwinia amylovora
• fire blight
• pollinators