Fusarium head blight (FHB) has reemerged as one of the most significant problems affecting wheat worldwide. Polygalacturonase (PG) is an important pectolytic enzyme produced by Fusariumspecies during the infection and colonistation in wheat plants. In this work, the correlationbetween in vitropolygalacturonase (PG) activityand aggressiveness of 15 Fusarium isolates (6 F.culmorum, 6 F. verticillioides and 3 F. solani) was investigated. Isolatesaggressivenesswereevaluated as the percentageof symptomatic spikelets perspike. In addition, isolates ability to produce in vitroPG activities were compared when grown ona solid medium. Aggressive isolates released more PGthanweakly aggressive isolates. Correlation analysis revealed a significant relationship (r = 0.57, r = 0.60, r = 0.64; P< 0.01; and r = 0.51, r = 0.64, r = 0.81; P< 0.01) between the PG produced by F. culmorum,F. verticillioidesand F. solani isolates and theiraggressiveness on the two wheat cultivars Cham4 and Hourani, respectively. On the other hand, no correlation was found between the PG production and the origin of the isolates. The datademonstrate that production of PGcould influence the aggressiveness of Fusarium spp. isolates towards wheat heads.
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