Characterization of Fusarium culmorum isolates by mycotoxin production and aggressiveness to winter wheat

Abstract

Twenty seven isolates of Fusarium culmorum were investigated for their aggressiveness on ears and leaves of wheat as well as for mycotoxin production by inoculating winter wheat (cv. Contra) in field trials conducted at Hennef, Germany, in 1996 . Additionally, in vitro mycotoxin production was determined on autoclaved cracked corn [maize]. Head blight and the negative effect of F. culmorum on 1000-grain weight greatly varied among isolates (30-90% of ears bleached; 14-61% reduction of 1000-grain weight). Aggressiveness as measured by 1000-grain weight reduction was not correlated to disease severity on wheat leaves. The more aggressive isolates produced mainly deoxynivalenol [vomitoxin] (DON) while the less aggressive isolates produced mainly nivalenol (NIV), further supporting involvement of DON in pathogenicity. Sixteen out of 27 isolates produced mainly NIV, 10 produced mainly DON and 1 produced both, NIV and DON. The DON-producing strains also produced 3-acetyldeoxynivalenol (3-ac-DON) in vitro. However, only one isolate produced NIV, DON and 3-ac-DON in vitro. Chemotaxonomy of F. culmorum into NIV- and DON-chemotypes is, therefore, suggested. In vivo mean NIV and DON contents were 34.7 mg/kg (range 0.95 to 55.2) and 40.8 mg/kg (range 2.9 to 74.3), respectively. The in vitro mean levels of NIV, DON and 3-ac-DON were 96.1 mg/kg (range 26.2 to 220.6), 77.7 mg/kg (range 27.2 to 180.8) and 230.7 mg/kg (range 64.7 to 548.7), respectively. DON content in vivo was positively correlated (r=0.762) to DON production in vitro while in vivo to in vitro nivalenol levels had a positive correlation of 0.455. In vitro DON and 3-ac-DON levels were highly positively correlated (r=0.994). Zearalenone could only be detected in vitro, with all but two strains producing detectable levels (mean 7.9 mg/kg, range 0.2 to 68.3).