An endophyte of Macrochloa tenacissima (esparto or needle grass) from Tunisia is a novel species in the Fusarium redolens species complex

Authors: GARGOURI, SAMIA - Tunisian National Institute Of Agronomy; BALMAS, VIRGILIO - University Of Sassari; BURGESS, LESTER - University Of Sydney; Paulitz, Timothy; LARABA, IMANE - Orise Fellow; Kim, Hye-Seon; Proctor, Robert; Busman, Mark; Felker, Frederick; MURRAY, TIMOTHY - Washington State University; O Donnell, Kerry

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2020
Publication Date: 6/18/2020
Citation: Gargouri, S., Balmas, V., Burgess, L., Paulitz, T., Laraba, I., Kim, H.-S., Proctor, R.H., Busman, M., Felker, F.C., Murray, T., O'Donnell, K. 2020. An endophyte of Macrochloa tenacissima (esparto or needle grass) from Tunisia is a novel species in the Fusarium redolens species complex. Mycologia. 112(4):792-807. https://doi.org/10.1080/00275514.2020.1767493.
DOI: https://doi.org/10.1080/00275514.2020.1767493

Interpretive Summary: Needle grass (Macrochloa tenacissima) is an economically important plant native to several Mediterranean countries in northern Africa, Spain, Portugal and southern France. The fiber produced from this species is used extensively for making paper, rope and various crafts. Agricultural Research Scientists at the National Center for Agricultural Utilization Research and colleagues in Tunisia and Italy discovered and characterized a novel Fusarium species growing in and on the roots of this grass. Because Fusarium includes many species that produce toxins that pose health risks to humans and other animals, the ability of this novel fungus and two closely related Fusarium species to produce toxins was assessed by chemical analyses of strains grown on cracked corn. These analyses revealed that all three species could produce two harmful toxins, beauvericin and enniatin B1. These research findings will be of interest to diverse agricultural scientists who are focusing on minimizing the exposure and risk that Fusarium toxins pose to human and plant health.

Technical Abstract: Here we report on the morphological, molecular and chemical characterization of a novel Fusarium species recovered from the roots and rhizosphere of Macrochloa tenacissima (Halfa, esparto or needle grass) in central Tunisia. Formally described here as F. spartum, this species is a member of the Fusarium redolens species complex, but differs from the other two species within the complex, F. redolens and F. hostae, by its endophytic association with M. tenacissima, and its genealogical exclusivity based on multilocus phylogenetic analyses. To assess their sexual reproductive mode, a uniplex PCR assay was designed and used to screen the three strains of F. spartum, 51 of F. redolens and 14 of F. hostae for mating type (MAT) idiomorph. Genetic architecture of the MAT locus in the former two species suggests that if they reproduce sexually it is via obligate outcrossing. By comparison, results of the PCR assay indicated that 13/14 of the F. hostae strains possessed MAT1-1 and MAT1-2 idiomorphs and thus might be self-fertile or homothallic. However, when the F. hostae strains were selfed, 11 failed to produce perithecia and one only produced several small abortive perithecia. Cirrhi, however, were only produced by 8/28 and 4/84 of the variable size perithecia, respectively, of F. hostae NRRL 29888 and 29890. The potential for the three F. redolens clade species to produce mycotoxins, pigments and phytohormones was assessed by screening whole genome sequence data and by analyzing extracts on cracked maize kernel cultures via liquid chromatography-mass spectrometry.