Cell wall‐degrading enzymes produced in vitro by isolates of Phaeosphaeria nodorum differing in aggressiveness

The relationships between in vitro production of cell wall‐degrading enzymes and aggressiveness of three Phaeosphaeria nodorum isolates were investigated. When grown in liquid medium containing 1% cell wall from wheat leaves as the carbon source, the isolates secreted xylanase, α‐arabinosidase, β‐xylosidase, polygalacturonase, β‐galactosidase, cellulase, β‐1,3‐glucanase, β‐glucosidase, acetyl esterase and butyrate esterase. Time‐course experiments showed different levels of enzyme production and different kinetics between isolates. A highly aggressive isolate produced more xylanase, cellulase, polygalacturonase and butyrate esterase than did the two weakly aggressive isolates. Xylanase was the most active polymer‐degrading enzyme produced, suggesting a key role during pathogenesis by P. nodorum .