Phylogenetic diversity, trichothecene potential, and pathogenicity within Fusarium sambucinum species complex

Authors: LARABA, IMANE - Orise Fellow; McCormick, Susan; Vaughan, Martha; GEISER, DAVID - Pennsylvania State University; O Donnell, Kerry

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2020
Publication Date: 1/12/2021
Citation: Laraba, I., McCormick, S.P., Vaughan, M.M., Geiser, D.M., O'Donnell, K. 2021. Correction: Phylogenetic diversity, trichothecene potential, and pathogenicity within Fusarium sambucinum species complex. PLoS ONE. 16(4). Article e0250812. https://doi.org/10.1371/journal.pone.0250812.
DOI: https://doi.org/10.1371/journal.pone.0250812

Interpretive Summary: Plant pathogenic molds pose a perennial threat to agricultural production and food safety and are responsible for multibillion-dollar annual losses to U.S. agriculture. These economic losses are often compounded by contamination of food and feed with fungal toxins that render diverse commodities unsuitable for consumption by humans and other animals. Trichothecene toxins produced by some species within the mold Fusarium are among the greatest concern to agriculture biosecurity, food safety, and human health because they can cause neurologic, gastrointestinal, immunological, and other serious health problems. Some of the world’s most economically destructive toxin-producing plant pathogens belong to a large group of related Fusarium species referred to as the Fusarium sambucinum complex. We developed DNA fingerprinting methods to rapidly identify the pathogens within this group of fungi and determined which toxins they could produce. A robust molecular surveillance program is essential to prevent the inadvertent introduction of these pathogens. Accurate identification of new pathogens and their potential to produce toxins will aid agricultural biosecurity and food safety within the U.S.

Technical Abstract: The Fusarium sambucinum species complex (FSAMSC) is one of the most taxonomically challenging groups of fusaria, comprising prominent mycotoxigenic plant pathogens and other species with various lifestyles. Among toxins produced by members of the FSAMSC, trichothecenes pose the most significant threat to public health. Herein a global collection of 171 strains, originating from diverse hosts or substrates, were selected to represent FSAMSC diversity. This strain collection was used to assess their species diversity, evaluate their potential to produce trichothecenes, and cause disease on wheat. Maximum likelihood and Bayesian analyses of a combined 3-gene dataset used to infer evolutionary relationships revealed that the 171 strains originally received as 48 species represent 74 genealogically exclusive phylogenetically distinct species distributed among six strongly supported clades: Brachygibbosum, Graminearum, Longipes, Novel, Sambucinum, and Sporotrichioides. Most of the strains produced trichothecenes in vitro but varied in the type synthesized, indicating that the six clades correspond to type A, type B, or both types of trichothecene-producing lineages. Furthermore, five strains representing two putative novel species within the Sambucinum Clade produced two newly discovered type A trichothecenes, 15-keto NX-2 and 15-keto NX-3. Strains of the two putatively novel species together with members of the Graminearum Clade were aggressive toward wheat when tested for pathogenicity on heads of the susceptible cultivar Apogee. In planta, the Graminearum Clade strains produced nivalenol or deoxynivalenol and the aggressive Sambucinum Clade strains synthesized NX-3 and 15-keto NX-3. Other strains within the Brachygibbosum, Longipes, Novel, Sambucinum, and Sporotrichioides Clades were nonpathogenic or could infect the inoculated floret without spreading within the head. Moreover, most of these strains did not produce any toxin in the inoculated spikelets. These data highlight aggressiveness toward wheat appears to be influenced by the type of toxin produced and that it is not limited to members of the Graminearum Clade.