Pseudomonas syringae as a microbial antagonist of Ceratocystis ulmi in the apoplast of American elm

Abstract

Isolates of Pseudomonas syringae are antagonistic to Ceratocystis ulmi, the causal agent of Dutch elm disease. P. syringae grows and produces antimycotics on expressed elm sap and on an extract of elm wood. When specific isolates of P. syringae, designated M27m and M323m, were introduced into the apoplast of greenhouse-grown elm seedlings, they established themselves without significant phytotoxicity and suppressed the development of vascular discolouration due to Dutch elm disease.