Crown and root rot of wheat, caused by Fusarium spp., limit crop yields worldwide, from rotting of seeds, seedlings, crowns, roots and basal plant stems. Virulence factors and virulence and aggressiveness of Fusarium spp. were investigated for isolates from Iran, obtained from wheat plants with crown and root rot symptoms. Forty isolates of Fusarium were used in this research. Among the isolates, nivalenol -NIV- was detected as the dominant trichothecene chemotype produced. Production of trichothecenes and zearalenone -ZEA- in autoclaved rice cultures of Fusarium isolates was analyzed using high performance liquid chromatography. The levels of NIV ranged from 258 to 1246 μg kg−1, of deoxynivalenol -DON- from 45 to 1411 μg kg−1, and of ZEA from 53 to 3220 μg kg−1. All Fusarium isolates produced cellulase and pectinase enzymes. Positive correlation was observed between activity of cell wall degrading enzymes -CWDEs- produced by the isolates and their pathogenicity on wheat leaf segments. Virulence of trichothecene-producing isolates was greater than that of nontrichothecene- producing isolates. Considerable association was detected between the capability of Fusarium spp. isolates to produce virulence factors -such as mycotoxins and CWDEs- and their pathogenicity on wheat.

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