Correlative Analysis of Cochliobolus sativus Pathogenicity and in vitro Xylanase Activity

Spot blotch (SB) caused by Cochliobolus sativus has been the major yield‐reducing factor for barley production during the last decade. In this study, the correlation between aggressiveness and in vitro xylanase production of 29 isolates of C. sativus was investigated. Isolate aggressiveness was evaluated in term of lesion form in barley leaves. Additionally, the isolates were compared for their ability to produce in vitro significant levels of xylanase activities when grown in a liquid medium. Aggressive isolates released more xylanase of weakly aggressive isolates. Correlation tests analysis revealed a significant relationship (r = 0.84, r = 0.50; P < 0.01) between the xylanase (per unit fungal mass) and aggressiveness on the two barley cultivars Arabi Abiad and Bowman, respectively. Correlation between the production of this enzyme and the origin of the isolates was not found. The results indicate that the production of xylanase influences the aggressiveness of the isolates of C. sativus towards barley seedlings.