CHARACTERIZATION OF THE FUNGUS INFESTING RYEGRASS PASTURES.

The research work explores the facial eczema problem in dairy cattle in the Eastern Cape, with the focus on the fungus Pseudopithomyces chartarum which infests primarily ryegrass. The characterization aims to: resolve the taxonomy of the genus Pseudopithomyces with the focus on Pseudopithomyces chartarum and to determine which species are associated with facial eczema; determine whether Pseudopithomyces chartarum is seed-borne; determine which Pseudopithomyces species predominate the outbreak areas in the Eastern Cape; study the relationship between sporidesmin production and the population diversity of Pseudopithomyces chartarum. The research is a joint investigation between FABI at the University of Pretoria and several institutions in New Zealand where the facial eczema problem is even more pronounced.

In terms of resolving the taxonomy and determining which species predominates in the affected areas, a total of 337 strains of P. chartarum have been collected and a total of 1737 sequences have been generated to date.  These include sequences for the following gene regions: ITS (n=346), Ben A (n=320), RPB2 (n=74), LSU (n=330), TEF (n=333) and GAPDH (n=334). Representative sequences were shared with Dr. Bevan Weir from New Zealand, who confirmed that there is only a single Pseudopithomyces species present in the five sampling regions here. Dr Weir also confirmed that the species present in the Eastern Cape group phylogenetically corresponds with the toxin producing species in New Zealand. From their most recent work, the New Zealand group now described the novel sporidesmin-producing species in the Pseudopithomyces species group as P. toxicarius. FABI consequently re-analyzed their 2019 collection of 67 isolates and found 64 to be P. toxicarius and three P. palmicola and in their most recent diversity study from the Eastern Cape, over 300 isolates were P. toxicarius. Preliminary investigations from the bordering Western Cape correspond.

It can be concluded that, similar to New Zealand, current thought here is that Pseudopithomyces toxicarius is the predominant sporidesmin-producing species in the coastal ryegrass-based pastures.