Species and Trichothecene Genotype of Pathogens Causing Fusarium Head Blight of Wheat in Nebraska, U.S.A.

Abstract

Fusarium head blight (FHB) is an economically important disease caused by several Fusarium species affecting wheat and other small grain cereals. In recent years, reports of shifts in populations of FHB pathogens around the world have shown that these populations are dynamic and change continuously, often resulting in increased yield losses or changes in the mycotoxins produced in the grain, which highlights the need for increased vigilance. The objective of this research was to identify the species and trichothecene genotypes of FHB pathogens in Nebraska in order to monitor their populations and the major toxigenic risks in the state. A total of 74 single-spore Fusarium isolates were obtained from 42 FHB-symptomatic wheat spikes collected from Nebraska fields during the growing seasons in 2015 to 2018. Most of the isolates were identified as F. graminearum (n = 67) based on translation elongation factor 1α (TEF1), trichothecene 3-O-acetyltransferase (TRI101), and reductase (RED) sequences. Additional species included F. boothii (n = 3), F. poae (n = 2), F. acuminatum (n = 1), and one isolate was an F. graminearum × F. boothii interspecific hybrid. All F. graminearum and F. boothii isolates had the 15-ADON trichothecene genotype. This study shows that F. graminearum is not the only pathogen causing FHB in Nebraska and helps expand knowledge on the worldwide distribution of F. boothii. The information obtained from this survey will be useful in developing effective FHB management strategies in Nebraska, because different pathogen populations can cause varying levels of disease intensity and can be selectively sensitive to management tactics.