The distribution and type B trichothecene chemotype of Fusarium species associated with head blight of wheat in South Africa during 2008 and 2009

Authors: VAN COLLER, GERHARDUS - Stellenbosch University; ROSE, LINDY - Stellenbosch University; BOUTIGNY, ANNE-LAURE - Stellenbosch University; Ward, Todd; LAMPRECHT, SANDRA - Agricultural Research Council Of South Africa; VILJOEN, ALTUS - Stellenbosch University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2022
Publication Date: 9/26/2022
Citation: Van Coller, G.J., Rose, L.J., Boutigny, A., Ward, T.J., Lamprecht, S.C., Viljoen, A. 2022. The distribution and type B trichothecene chemotype of Fusarium species associated with head blight of wheat in South Africa during 2008 and 2009. PLOS ONE. 17(9). Article e0275084. https://doi.org/10.1371/journal.pone.0275084.
DOI: https://doi.org/10.1371/journal.pone.0275084

Interpretive Summary: Fusarium head blight (FHB) is a 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. As part of a project to establish a global picture of FHB pathogen diversity, we determined the prevalence of Fusarium species and toxin-types associated with FHB infected wheat in South Africa. In the largest analysis to date, we identified 24 species from seven Fusarium species complexes among FHB-infected wheat in South Africa. These results greatly expand the known species diversity associated with FHB in South Africa, and include the first report of F. acuminatum, F. armeniacum, F. avenaceum, F. temperatum, and F. pseudograminearum from wheat heads in South Africa. Globally, it is also the first report of F. brachygibbosum, F. lunulosporum and F. transvaalense from wheat. In addition, potentially novel species were identified within six Fusarium species complexes. As such, the results reported here are critical to promoting food safety and cereal production through plant quarantine and variety improvement efforts that account for the entire spectrum of FHB pathogens and toxin types.

Technical Abstract: Fusarium head blight (FHB) of wheat occurs commonly in irrigation regions of South Africa and less frequently in dryland regions. Previous surveys of Fusarium species causing FHB identified isolates using morphological characters only. This study reports on a comprehensive characterisation of FHB pathogens conducted in 2008 and 2009. Symptomatic wheat heads were collected from the Northern Cape, KwaZulu-Natal (KZN), Bushveld and eastern Free State (irrigation regions), and from one field in the Western Cape (dryland region). Fusarium isolates were identified with species-specific primers or analysis of partial EF-1a sequences. A representative subset of isolates was characterized morphologically. In total, 1047 Fusarium isolates were collected, comprising 24 species from seven broad species complexes. The F. sambucinum (FSAMSC) and F. incarnatum-equiseti species complexes (FIESC) were most common (83.5% and 13.3% of isolates, espectively). The F. chlamydosporum (FCSC), F. fujikuroi (FFSC), F. oxysporum (FOSC), F. solani (FSSC), and F. tricinctum species complexes (FTSC) were also observed. Within the FSAMSC, 90.7% of isolates belonged to the F. graminearum species complex (FGSC), accounting for 75.7% of isolates. The FGSC was the dominant Fusaria in all four irrigation regions. F. pseudograminearum dominated at the dryland field in the Western Cape. The Northern Cape had the highest species diversity (16 Fusarium species from all seven species complexes). The type B trichothecene chemotype of FGSC and related species was inferred with PCR. Chemotype diversity was limited (15-ADON = 90.1%) and highly structured in relation to species differences. These results expand the known species diversity associated with FHB in South Africa and include first reports of F. acuminatum, F. armeniacum, F. avenaceum, F. temperatum, and F. pseudograminearum from wheat heads in South Africa, and of F. brachygibbosum, F. lunulosporum and F. transvaalense from wheat globally. Potentially novel species were identified within the FCSC, FFSC, FOSC, FSAMSC, FIESC and FTSC.