Frequency of the nivalenol mycotoxin genotype in Fusarium graminearum sampled from North Carolina wheat fields

Authors: NILSSON, KATHRYN - North Carolina State University; Cowger, Christina

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/22/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fusarium head blight (or scab), caused primarily by F. graminearum in the U.S., leads to drastic decreases in yield and test weight of small grains. In addition, Fusarium mycotoxins in grain heads can render the crop unsuitable for human or animal consumption. In livestock, scabby grain can lead to feed refusal and/or poor weight gain. Although this fungus produces various mycotoxins, the most important ones in small grains are deoxynivalenol (DON) and nivalenol (NIV). Both can cause severe illnesses in humans and livestock; compared to DON, NIV is more toxic to mammals. While DON is the dominant wheat scab toxin in most of the U.S., a high proportion of Fusarium isolates from southern Louisiana wheat had been found to be NIV producers. Although a previous wheat survey detected about 10% NIV producers in each of two NC counties, the distribution of NIV strains across the state was unknown. DON contamination is often measured in North Carolina grain crops, but NIV is not. In this study, we sampled commercial wheat heads symptomatic for scab from 13 fields in 7 NC counties. From each infected head, a single Fusarium strain was created and testedto determine if it was a DON or a NIV producer. In some fields, 5-10% of strains were found to be NIV producers. By estimating the distribution of NIV-producing Fusarium strains in North Carolina wheat fields, we will determine whether and where NIV may warrant monitoring in severe scab years.

Technical Abstract: In the U.S., Fusarium head blight (or scab) is caused primarily by F. graminearum. Fusarium mycotoxins in small grain heads can render the crop unsuitable for human or animal consumption. In livestock, scabby grain can lead to feed refusal and/or poor weight gain. Although this fungus produces various mycotoxins, the most important ones in small grains are deoxynivalenol (DON) and nivalenol (NIV). Both can cause severe toxicoses in humans and livestock; compared to DON, NIV has greater mammalian toxicity. While DON is the dominant wheat scab toxin in most of the U.S., a high proportion of Fusarium isolates from southern Louisiana wheat had been found to be NIV producers. Although a previous wheat survey detected about 10% NIV producers in each of two NC counties, the distribution of NIV strains across the state was unknown. DON contamination is often measured in North Carolina grain crops, but NIV is not. In this study, we sampled commercial wheat heads symptomatic for scab from 60 fields in 24 NC counties. From each infected head, a single Fusarium strain was isolated and tested using polymerase chain reaction (PCR) to determine if it was a DON or a NIV producer. Again, while the vast majority of strains were 15-ADON, and almost none were 3-ADON, in some fields 5-10% of strains were found to be NIV producers. By estimating the distribution of NIV-producing Fusarium strains in North Carolina wheat fields, we will determine whether and where NIV may warrant monitoring in severe scab years.