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Prof Botma Visser takes on rust diseases threatening South Africa’s wheat

09 September 2025 | Story Martinette Brits | Photo Stephen Collett

Safeguarding one of the world’s most vital staple foods was at the heart of the inaugural lecture delivered by Prof Botma Visser, Professor in the Department of Plant Sciences at the University of the Free State (UFS), on Wednesday 3 September 2025. Prof Visser shared insights from nearly two decades of research into wheat rust – a devastating crop disease that threatens both South Africa’s harvests and global food security.

“Wheat production in South Africa is threatened by three fungal pathogens that cause rust disease on the crop. Understanding the factors that contribute to virulence on locally grown cultivars is crucial to ensure continued wheat production,” said Prof Visser.

The fight against evolving wheat rusts

For the past 17 years, Prof Visser’s research has focused on the genetic structure of rust populations and the risks they pose to food security. His work has shown that these populations are dynamic and constantly changing due to genetic mutations within existing races, as well as the introduction of new races into South Africa.

“Computer modelling showed that rust can spread over vast distances by prevailing winds. During the 20th Century, at least four Southern African stem rust races managed to move across the Indian Ocean from Southern Africa to Australia. South Africa, in turn, received multiple new races from mid-Africa across Zambia and Zimbabwe, without any means of stopping these introductions,” he explained.

To respond to this challenge, his team recently implemented MARPLE (Mobile And Real-time Plant disEase) diagnostics using fourth-generation nanopore sequencing technology. This approach allows the rapid characterisation of fungal isolates, specifically targeting genes linked to fungicide resistance and virulence.

“This work,” Prof Visser noted, “is part of an effort to safeguard global wheat production.”

His research is a collaborative effort with Prof Willem Boshoff (Department of Plant Sciences, UFS) and Dr Tarekegn Terefe (Agricultural Research Council – Small Grain, Bethlehem). Together, their work has positioned the UFS as an internationally recognised centre of excellence in wheat rust research.

About Prof Botma Visser

Prof Botma Visser obtained his BSc in Botany and Microbiology (1988), BSc Honours in Microbiology (1989), and MSc in Botany (1993) at the University of the Free State, where he also completed his PhD in Botany in 2004.

His career spans more than 18 years of research into wheat rust pathogens, combining annual surveys, race pathotyping, molecular genetics, and cutting-edge sequencing technologies. His expertise has not only advanced understanding of rust population dynamics in South Africa but also contributed to global collaborative studies on crop disease.

News Archive

UFS study on cell development in top international science journal

2008-09-16

A study from the University of the Free State (UFS) on how the change in the packaging of DNA with cell development influenced the expression of genes, will be published in this week’s early edition of the prestigious international, peer-reviewed science journal, the Proceeding of the National Academy of Sciences of the USA (PNAS).

The PNAS journal has an impact factor of 10, which means that studies published in the journal are, on average, referred to by ten other scientific studies in a two year period. The South African Journal of Science, by comparison, has an impact factor of 0.7.

The UFS study, funded by the Wellcome Trust and the National Research Foundation (NRF), looked at how the change in the packaging of DNA with cell development influenced the expression of genes. It is very relevant to research on stem cells, an area of medicine that studies the possible use of undifferentiated cells to replace damaged tissue.

Prof. Hugh Patterton, of the Department of Microbial, Biochemical and Food Biotechnology at the UFS, who led the study, said: "We are extremely proud of this study. It was conceived in South Africa, it was performed in South Africa, the data were analysed in South Africa, and it was published from South Africa."

When a gene is expressed, the information encoded in the gene is used to manufacture a specific protein. In eukaryotes, which include humans, there is approximately 1m of DNA, containing the genes, in every cell. This length of DNA has to fit into a cell nucleus with a diameter of only about 10 micrometer. In order to fit the DNA into such a small volume, eukaryotic cells wrap their DNA onto successive protein balls, termed nucleosomes. Strings of nucleosomes, resembling a bead of pearls, is folded into a helix to form a chromatin fiber. The study from the UFS investigated how the binding of a specific protein, termed a linker histone, that binds to the length of DNA between nucleosomes, influenced the formation of the chromatin fiber and also the activity of genes.

"We found that the linker histone bound to chromatin in yeast, which we use as a model eukaryote, under conditions where virtually all the genes in the organism were inactive. It was widely believed that the binding of the linker histone caused the inactivation of genes. We studied the relationship between the amount of linker histone bound in the vicinity of each gene and the expression of that gene for all the genes in yeast, using genomic techniques. We made the surprising discovery that even through the linker histone preferentially bound to genes under conditions where the genes were shut off, this inactivation of genes was not caused by the binding of the linker histone and folding of the chromatin,” said Prof. Patterton.

He said: “Instead our data strongly suggested that the observed anti-correlation was due to the movement of enzymes along the DNA molecule, involved in processing the information in genes for the eventual manufacture of proteins. This movement of enzymes displaced the linker histones from the DNA. This finding now requires a rethink on aspects of how packaging of DNA influences gene activity."

Prof. Patterton said that his research group, using the Facility for Genomics and Proteomics as well as the Bioinformatics Node at the UFS, was currently busy with follow-up studies to understand how other proteins in nucleosomes affected the activities of genes, as well as with projects to understand how chemicals found in red wine and in green tea extended lifespan. "We are certainly having a marvelous time trying to understand the fundamental mechanisms of life, and the UFS is an exciting place to be if one was interested in studying life at the level of molecules," he said.

Media Release
Issued by: Lacea Loader
Assistant Director: Media Liaison
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl.stg@ufs.ac.za
18 September 2008

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