Date of this Version
Panthi, A. (2012). Characterization of Chemotype and Aggressiveness of Nebraska Isolates of Fusarium graminearum. MS thesis, University of Nebraska-Lincoln.
Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is a devastating disease of wheat and other small grain cereals. FHB lowers grain yield and quality and contaminates grain with mycotoxins, predominantly deoxynivalenol (DON) and its acetylated derivatives 3-ADON and 15-ADON. Forty one Fusarium isolates collected from grain elevators and wheat fields in Nebraska in 2009 and 2010 were sequenced for molecular identification. Forty isolates were identified as F. graminearum and one isolate was identified as F. culmorum. Seventy seven F. graminearum isolates collected from grain elevators and wheat fields in Nebraska from 2007 to 2010 were tested for DON production in vitro. All isolates produced DON in variable amounts. A multiplexed PCR assay was carried out to identify the chemotype of the 77 isolates. All 51 isolates that were amplified belonged to the 15-ADON chemotype. Sixteen selected isolates varied widely in mycelial characteristics, and DON and spore production in vitro. Mycelia were sparse in some isolates and dense in others. Mycelial color ranged from white to yellow to pale orange. Pigments formed by the isolates ranged in color from dark red to bright red to yellow. DON and spore concentrations ranged from low to high. Under greenhouse conditions, eight selected isolates - four of which produced DON at high levels and four at low levels in vitro - differed significantly (P ≤ 0.05) in aggressiveness on spikes and DON production in grain of FHB-susceptible spring wheat cultivar Wheaton. High DON producers (in vitro and in grain) were more aggressive than low-DON producers. DON concentration in vitro accurately predicted aggressiveness on wheat spikes and DON production in grain. It is concluded that in Nebraska, i) F. graminearum is the major cause of FHB, ii) the 15-ADON chemotype of the pathogen predominates, iii) variation exists among isolates of the pathogen in DON production, in vitro cultural characteristics, and aggressiveness on wheat spikes, and iv) DON production in vitro is an accurate prediction of DON production in planta and of aggressiveness.
Advisors: Stephen Wegulo and Heather Hallen-Adams