Many plant pathologists spend entire careers trying to outwit microbes, in particular those that cause diseases of economically important plants. In some cases control measures are simple and successful. In others, disease management remains an ongoing battle. 

Prof Zakkie Pretorius, Professor in the Department of Plant Sciences, works on a group of wheat diseases known as rusts. The name is derived from the powdery and brown appearance of these fungi.

Over the course of history wheat rusts have undergone what are notoriously known as boom and bust cycles. During boom periods the disease is controlled by means of heritable resistance in a variety, resulting in good yields. This resistance, though, is more often than not busted by the appearance of new rust strains with novel parasitic abilities. For resistance to remain durable, complex combinations of effective genes and chromosome regions have to be added in a single wheat variety.

In recent years, Prof Pretorius has focused on identifying and characterising resistance sources that have the potential to endure the onslaught of new rust races. His group has made great progress in the control of stripe rust – where several chromosome regions conditioning effective resistance have been identified.

Dr Renée Prins of CenGen and an affiliated UFS staff member, developed molecular markers for these resistance sources. These are now routinely applied in wheat breeding programmes in South Africa. In addition, Prof Pretorius collaborates with several countries to transfer newly discovered stem rust resistance genes to wheat, and in characterising effective sources of resistance in existing wheat collections.

His work is closely supported by research conducted by UFS colleagues, students and other partners on the genetics of the various wheat rust pathogens. These studies aim to answer questions about:
• the origin and relatedness of rust races,
• their highly successful parasitic ability, and
• their adaptation in different environments.

The UFS wheat rust programme adds significantly to the development of resistant varieties and thus more sustainable production of this important crop. 

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