Regional and field-specific differences in Fusarium species and mycotoxins associated with blighted North Carolina wheat

Worldwide, while Fusarium graminearum is the main causal species of Fusarium head blight (FHB) in small-grain cereals, a diversity of FHB-causing species belonging to different species complexes has been found in most countries. In the U.S., FHB surveys have focused on the Fusarium graminearum species complex (FGSC) and the frequencies of 3-ADON, 15-ADON, and nivalenol (NIV) chemotypes. A large-scale survey was undertaken across the state of North Carolina in 2014 to explore the frequency and distribution of F. graminearum capable of producing NIV, which is not monitored at grain intake points. Symptomatic wheat spikes were sampled from 59 wheat fields in 24 counties located in three agronomic zones typical of several states east of the Appalachian Mountains: Piedmont, Coastal Plain, and Tidewater. Altogether, 2197 isolates were identified to species using DNA sequence-based methods. Surprisingly, although F. graminearum was the majority species detected, species in the Fusarium tricinctum species complex (FTSC) that produce “emerging mycotoxins” were frequent, and even dominant in some fields. The FTSC percentage was 50–100% in four fields, 30–49% in five fields, 20–29% in five fields, and