Comparison ofmalusinfection by the pathogenerwinia amylovoraand colonisation by the saprophyteerwinia herbicolaby electron microscopy

Abstract

Abstract Erwinia amylovora infection of either apple stem or leaf tissue resulted in xylem occlusion by a fibrillar matrix material, determined by Thiery’ s thiocarbohydrazide (TCH) test to be the extracellular polysaccharide from E. amylovora. Plasmolysis of the xylem‐parenchyma was also detected and was most likely a result of a toxin produced by the pathogen. This plasmolysis resulted in the collapse and death of the cell. An Erwinia herbicola isolate which had previously expressed inhibitory effects on E. amylovora was contained at the site of inoculation.