Taxonomy of species within the Gibberella fujikuroi complex

Abstract

Fusarium was established to accommodate phialidic fungi with fusiform macroconidia borne on poly- or monophialides. They are characterised by significant variation in morphological characters. These morphological characteristics have been used as basis to demarcate species within the genus with a wide host range and cosmopolitan distribution. In the first chapter these morphological characters and other criteria used to demarcate species in the genus Fusarium are reviewed. Furthermore the predominant three species concepts applied to Fusarium are discussed. The second chapter of the thesis deals with polyphyletic nature pertaining to F. subglutinans sensu lato. This study was based on informative morphological characters as well as sequence data obtained from the translation elongation factor 1 , -tubulin and 28S regions of the rDNA gene region. The results indicate that F. subglutinans sensu lato represents at least thirteen independent species associated with a variety of hosts. This manuscript was submitted for peer-viewing. In the third chapter the taxonomic placement of a new Fusarium species from Poaceae, in South Africa is considered. Both morphological and molecular characters were used to determine the relationship of the new species to other species in the F. subglutinans sensu lato species complex and more specifically the two species, F. subglutinans sensu stricto and F. circinatum, with which it formed fertile sexual crosses. The Fusarium sp. isolated from Poaceae was described as Fusarium ophiodes sp. nov. This manuscript was submitted for peer-viewed. In the fourth chapter the causal agent of pine decline in Chilean nurseries are characterised as Fusarium ciricinatum. This was done by means of sexual crosses, phylogenetics and morphological comparisons. This led to the first report of the disease in Chile with different aspects published as two peer-reviewed articles. The last chapter deals with the generic placement of a new Fusarium species associated with Ananas comosus. The species was described as F. ananatum. It displays salmon colony colour with conidia produced by means of both poly- and monophialides. The erect aerial mycelium distinguishes it from the closely related species, F. guttiforme. Based on the sequence data obtained from the translation elongation factor 1 , -tubulin and histone 3 genes, this species represent a new species in F. subglutinans sensu lato. The study resulted in a peer-reviewed publication.