Species composition, toxigenic potential and aggressiveness of Fusarium isolates causing Head Blight of barley in Uruguay

Authors: GARMENDIA, GABRIELA - Universidad De La República; PATTARINO, LUCIANA - Universidad De La República; NEGRIN, CAMILA - Universidad De La República; MARTINEZ, ADALGISA - Universidad De La República; PEREYRA, SILVIA - National Agricultural Research Institute(INIA); Ward, Todd; VERO, SILVANA - Universidad De La República

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2018
Publication Date: 7/12/2018
Citation: Garmendia, G., Pattarino, L., Negrin, C., Martinez-Silveira, A., Pereyra, S., Ward, T.J., Vero, S. 2018. Species composition, toxigenic potential and aggressiveness of Fusarium isolates causing Head Blight of barley in Uruguay. Food Microbiology. 76:426-433. https://doi.org/10.1016/j.fm.2018.07.005.
DOI: https://doi.org/10.1016/j.fm.2018.07.005

Interpretive Summary: Fusarium head blight (FHB) is a destructive disease of cereals crops worldwide and a major food safety concern because FHB pathogens can contaminate grain with trichothecenes and other fungal toxins (mycotoxins). FHB is caused by a diverse set of fungal species that make different mycotoxins. Understanding which FHB species and toxin types are present in an area is key to disease and mycotoxin control programs. In this study, ARS scientists in Peoria, IL, worked in collaboration with scientists in Uruguay to identify and characterize FHB pathogens from barley. Fusarium graminearum with the ability to make a form of vomitoxin called 15-acetyldeoxynivalenol (15-ADON) were identified as the most common FHB pathogens of barley, although a number of other pathogen species were detected for the first time on barley from Uruguay. Analyses of genetic diversity revealed that wheat and barley share a common FHB pathogen population that moves back and forth between these two hosts. The different FHB pathogens obtained in this study exhibited different levels of aggressiveness toward barley and different levels of resistance to two commonly used fungicides. These results provide new information on FHB pathogen and mycotoxin prevalence, host distributions, aggressiveness, and fungicide sensitivity that can be used to develop regionally targeted disease and mycotoxin control programs that improve crop production and food safety.

Technical Abstract: Fusarium Head Blight (FHB) is a major constraint to barley production that substantially reduces yield and grain quality. FHB is also a major food safety concern because FHB pathogens contaminate grain with trichothecenes and other mycotoxins. DNA sequence-based analyses and in-vitro toxin assessments were used to characterize the species and trichothecene chemotype composition of FHB pathogens on barley in Uruguay. F. graminearum was the dominant species (89.7%), and three other members of the F. graminearum species complex (FGSC) were identified as FHB pathogens of barley in Uruguay for the first time. Other minor contributors to FHB species diversity included F. poae, F. avenaceum, F. pseudograminearum and an unnamed species from the F. incarnatum-equiseti species complex (FIESC). Most isolates (89.7%) had the 15-acetyldeoxynivalenol (15-ADON) trichothecene type. However, the results expanded the known area of occurrence within Uruguay for the nivalenol (NIV) toxin type, which was observed among isolates from three species of the FGSC, F. pseudograminearum, and F. poae. Isolates with the 3-acetyldeoxynivalenol (3-ADON) or NX-2 toxin types were not observed, although a previously published multilocus genotyping assay was updated to identify NX-2 strains. Analyses of population structure and comparisons with FHB isolates from wheat in Uruguay indicated that F. graminearum constitutes a single genetic population with no evidence of population differentiation related to the sampled hosts. Inter and intraspecific differences were observed in aggressiveness toward four barley genotypes with different levels of resistance to FHB, and in general nivalenol producers were the least aggressive isolates. Sensitivity to metconazole was approximately 10 times higher than was detected for tebuconazole. This is the first report regarding tebuconazole and metconazole sensitivity for Fusarium species causing FHB in barley in Uruguay, and constitutes an important starting point for monitoring temporal or spatial changes in FGSC sensitivity, which is critical to define FHB management practices.