Fusarium subtropicale sp. nov., a novel nivalenol mycotoxin-producing species isolated from barley (Hordeum vulgare) in Brazil and sister to F. praegraminearum

Authors: PEREIRA, CAROLINA - University Of Maringa; Ward, Todd; TESSMANN, DAURI - Universidade Federal De Vicosa; DEL PONTE, EMERSON - Universidade Federal De Vicosa; Vaughan, Martha; McCormick, Susan; Busman, Mark; Kelly, Amy; Proctor, Robert; LARABA, IMANE - National Higher School Of Agronomy; O Donnell, Kerry

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2018
Publication Date: 10/10/2018
Citation: Pereira, C.B., Ward, T.J., Tessmann, D.J., Del Ponte, E.M., Laraba, I., Vaughan, M.M., McCormick, S.P., Busman, M., Kelly, A., Proctor, R.H., O'Donnell, K. 2018. Fusarium subtropicale sp. nov., a novel nivalenol mycotoxin-producing species isolated from barley (Hordeum vulgare) in Brazil and sister to F. praegraminearum. Mycologia. 110(5):860-871. https://doi.org/10.1080/00275514.2018.1512296.
DOI: https://doi.org/10.1080/00275514.2018.1512296

Interpretive Summary: The present pathogen survey was conducted in commercial wheat and barley fields in the major production regions of Paraná State during 2011 through 2015 to identify and monitor areas where Fusarium head blight (FHB) of small grain cereals incidence was high. The molecular data used to identify the 754 isolates suggested that one strain (F1478 = NRRL 66764) collected from a barley field in Guarapuava, Paraná State in 2013 might represent a novel FHB pathogen. Therefore, the present study was conducted to collect and analyze DNA sequence data from portions of 10 genes to assess whether this isolate represented a novel species and to infer its closest relatives. Because the genetic analysis of the DNA data indicated isolate NRRL 66764 was a novel FHB pathogen, morphological data was collected and used to formally describe it as Fusarium subtropicale. The potential of this isolate to produce toxins was predicted from whole-genome sequence data. When it was grown in liquid broth and on cracked corn, F. subtropicale produced several toxins. Lastly, in a plant pathogenicity experiment, F. subtropicale induced FHB in susceptible wheat cultivar “Norm” and contaminated the plants with toxins. Because this novel toxin-producing cereal pathogen poses a threat to agricultural production and food safety, the results of this study should be of interest to quarantine officials, toxicologists, and plant pathologists who are focused on developing robust strategies to minimize the threat of FHB worldwide.

Technical Abstract: Surveys were conducted in commercial wheat and barley fields in the southcentral production regions of State of Paraná, Brazil from 2011 through 2015. Spikes displaying visible Fusarium head blight symptoms were collected and the pathogen isolated from the tissues. The 754 Fusarium isolates recovered were identified by a high-throughput multilocus genotyping assay (MLGT) designed to identify trichothecene toxin-producing fusaria (i.e. formerly B-clade, but referred to here as F. sambucinum species complex lineage 1 [FSAMSC-1]) together with sequencing a portion of the translation elongation factor 1-a (TEF1) gene. One strain was discovered that appeared to be closely related to but phylogenetically distinct from F. praegraminearum based on the relatively low 97.7% TEF1 identity and positive genotype obtained with one of the two F. praegraminearum species-specific MLGT probes. Molecular phylogenetic analyses of a 10-gene dataset resolved this novel FSAMSC-1 species and F. praegraminearum as sisters. Formally described herein as F. subtropicale, it is phenotypically distinct from the 22 other FSAMSC-1 species in that it produces mostly 1-to-3-septate macroconidia. Whole-genome sequence data was used to predict its potential to produce mycotoxins. Chemical analyses confirmed F. subtropicale could produce the mycotoxins 4, 15-diacetylnivalenol, butenolide, culmorin and fusarin C in vitro and the pathogenicity experiment revealed F. subtropicale could infect but not spread in susceptible hard red spring wheat cultivar “Norm.”