Two new species ofFusarium: Fusarium brevicatenulatumfrom the noxious weedStriga asiaticain Madagascar andFusarium pseudoanthophilumfromZea maysin Zimbabwe

Characterisation, pathogenicity and hydrolytic enzyme profiling of selected Fusarium species and their inhibition by novel coumarins

Three Fusarium species isolated locally were characterised by the amplification of their rDNA ITS region, host specificity, and hydrolytic enzyme production. The strains were identified as Fusarium pseudoanthophilum, which is being reported for the first time in South Africa, as well as F. foetens and F. fujikuroi. All the three strains were capable of infecting vegetables such as tomatoes, bell and cayenne peppers, belonging to the Solanaceae family. The Fusarium strains also showed significant production of cell wall degrading enzymes in vitro, such as amylase, cellulase, xylanase, and polygalacturonase, thus highlighting the possibilities of these enzymes as pathogenic factors. Subsequently, the strains were discovered to be susceptible to three halogenated coumarins. The most effective of the tested coumarins, 6-bromo3-2,2-dibromoacetyl-2H-chromen-2-one, showed MIC values of 0.125, 0.0625 and 0.125 mg/ml against F. foetens, F. pseudoanthophilum and F. fujikuroi, respectively. The antifungal potentials of the halogenated coumarins were confirmed in silico through PASS analysis, toxicity prediction and docking studies. Findings from this study demonstrate the use of these coumarins as potential control agents against the Fusarium species and other pathogenic fungi in general.

Phylogenetically Diverse Fusarium Species Associated with Sorghum (Sorghum Bicolor L. Moench) and Finger Millet (Eleusine Coracana L. Garten) Grains from Ethiopia

Fusarium is one of the most diverse fungal genera affecting several crops around the world. This study describes the phylogeny of Fusarium species associated with grains of sorghum and finger millet from different parts of Ethiopia. Forty-two sorghum and 34 finger millet grain samples were mycologically analysed. All of the sorghum and more than 40% of the finger millet grain samples were contaminated by the Fusarium species. The Fusarium load was higher in sorghum grains than that in finger millet grains. In addition, 67 test isolates were phylogenetically analysed using EF-1α and β-tubulin gene primers. Results revealed the presence of eight phylogenetic placements within the genus Fusarium, where 22 of the isolates showed a close phylogenetic relation to the F. incarnatum–equiseti species complex. Nevertheless, they possess a distinct shape of apical cells of macroconidia, justifying the presence of new species within the Fusarium genus. The new species was the most dominant, represented by 33% of the test isolates. The current work can be seen as an important addition to the knowledge of the biodiversity of fungal species that exists within the Fusarium genus. It also reports a previously unknown Fusarium species that needs to be investigated further for toxin production potential.

Gibberellin biosynthesis in fungi: genes, enzymes, evolution, and impact on biotechnology

Gibberellins (GAs) constitute a large family of tetracyclic diterpenoid carboxylic acids, some members of which function as growth hormones in higher plants. As well as being phytohormones, GAs are also present in some fungi and bacteria. In recent years, GA biosynthetic genes from Fusarium fujikuroi and Arabidopsis thaliana have been cloned and well characterised. Although higher plants and the fungus both produce structurally identical GAs, there are important differences indicating that GA biosynthetic pathways have evolved independently in higher plants and fungi. The fact that horizontal gene transfer of GA genes from the plant to the fungus can be excluded, and that GA genes are obviously missing in closely related Fusarium species, raises the question of the origin of fungal GA biosynthetic genes. Besides characterisation of F. fujikuroi GA pathway genes, much progress has been made in the molecular analysis of regulatory mechanisms, especially the nitrogen metabolite repression controlling fungal GA biosynthesis. Basic research in this field has been shown to have an impact on biotechnology. Cloning of genes, construction of knock-out mutants, gene amplification, and regulation studies at the molecular level are powerful tools for improvement of production strains. Besides increased yields of the final product, GA3, it is now possible to produce intermediates of the GA biosynthetic pathway, such as ent-kaurene, ent-kaurenoic acid, and GA14, in high amounts using different knock-out mutants. This review concentrates mainly on the fungal biosynthetic pathway, the genes and enzymes involved, the regulation network, the biotechnological relevance of recent studies, and on evolutionary aspects of GA biosynthetic genes.

Pini represents a distinct mating population in the gibberella fujikuroi species complex

Fusarium strains in the Gibberella fujikuroi species complex cause diseases on a variety of economically important plants. One of these diseases, pitch canker of Pinus spp., is caused by strains identified as Fusarium subglutinans f. sp. pini. Fertile crosses were detected between F. subglutinans f. sp. pini strains from South Africa, California, and Florida. F. subglutinans f. sp. pini strains were not cross-fertile with the standard tester strains of six of the seven other mating populations of G. fujikuroi. Sporadic perithecia with ascospores were obtained in two crosses with the mating population B tester strains. These perithecia were homothallic, and the ascospores derived from these perithecia were vegetatively compatible with the mating population B tester strain parent. We concluded that fertile F. subglutinans f. sp. pini isolates represent a new mating population (mating population H) of G. fujikuroi and that they belong to a unique biological species in a distinct taxon.