Miss Ariska Van der Nest

MSc Student

Research Interests

I am interested in the field of mycotoxicology. South Africa could greatly benefit from an improved knowledge on the subject as this could lead to the improvement of food quality and safety in our country.

My honours project focused on the mycotoxigenic fungi that occur in animal feed in Southern Africa. Although only regulations against levels of aflatoxins in animal feed are instated, it is known that other mycotoxins are also associated with these commodities. The aim of this study was to determine the levels of mycotoxigenic fungi associated with various animal feed products available in South Africa. I did not only obtained sound knowledge on the morphological identification of fungi that occurred on the animal feed tested, but also obtained knowledge on how to enumerate fungi occurring in a commodity. This study indicated that significant numbers of a wide variety of fungi such as Aspergillus and Penicillium species were present in the animal feed. The presence of these fungi indicates that mycotoxins such as aflatoxins, moniliformin, sterigmatocystin, tenuazonic acid, rhizonin A and tremorgens could likely be present in the animal feed.

My MSc project focuses on the fungus Phoma sorghina. This fungus is a seed- and soil-borne inhabitant that is known as a secondary invader of weak or diseased plants but is mainly associated with sorghum and millet. P. sorghina is known to produce tenuazonic acid that causes the inhibition of protein synthesis when consumed. This fungus is also the producer of an unknown mycotoxin that causes a disease called onyalai in individuals that eat grains contaminated with P. sorghina. This diseases is characterized by the formation of blood blisters in the mouth and throat and is only geographically associated with Africa. As Phoma sorghina has a wide plant host range and is known to produce different mycotoxins, my study is focusing on whether this fungus represents a single species or if a complex of species occurs in South Africa.

Posters and Presentations

• Van der Nest, A., Marais, G.J., Lübben, A.  2006. Fungi and their mycotoxins associated with animal feed in South Africa. Abstracts of the 44^th Congress of the South African Society for Plant Pathology, Magalies Park Country Club, 22-25 January 2006. p74.
• Van der Nest, A., Marais, G.J., Lübben, A.  2006.  The role of mycotoxigenic fungi in commercially produced animal feed.  Abstracts of the 14^th Biennial Conference of the South African Society for Microbiology, CSIR International Convention Centre, 9 - 12 April 2006. p130.
• Van der Nest, A., Steenkamp, E.T., Marais, G.J. 2007.  Phoma sorghina: a review on the complexity of its taxonomy and ecological distribution.  Abstracts of the 45^th Congress of the South African Society for Plant Pathology, Kopanong, 21-24 January 2007. p 53.
• Van der Nest, A., Steenkamp, E.T., Marais, G.J.  2008. Phylogenetic diversity of Phoma sorghina in Southern Africa. Biennial Conference of the South African Society for Microbiology (Bio-08), Rhodes University, 21-22 January 2008.