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10 June 2020 | Story Leonie Bolleurs | Photo Supplied
Prof Zakkie Pretorius, left, plays a significant role in providing pathology support to the plant breeding industry.Prof Liezel Herselman contributes to plant breeding in Southern Africa by training and mentoring the plant breeders of the future.

The Southern African Plant Breeders’ Association (SAPBA) recently bestowed prestigious awards upon Prof Zakkie Pretorius, Research Fellow in the Department of Plant Sciences at the University of the Free State (UFS), and Prof Liezel Herselman, Associate Professor in the same department. This institution strives to maintain high ethical standards and norms, contributing to stable, sustainable agriculture.

During the 13th Southern African Plant Breeders’ Association symposium, Prof Herselman was presented with a Fellow Award and Prof Pretorius with Honorary Membership. They received the awards for their services to and promotion of the SAPBA objectives, together with their exceptional contributions to plant breeding. 

Provide food for the nation
Over the years, Prof Pretorius, who has extensive expertise in diseases of field crops – more specifically the rust diseases of small grain cereal crops – has played a significant role in providing pathology support to the plant breeding industry. He has also conducted ground-breaking pathology research on rust diseases in field crops. In 2019, he co-authored an article that appeared in Nature, the world’s leading multidisciplinary science journal. He is also shortlisted as a 2020 finalist in the Lifetime Award and Special Theme Award (Plant Health) of the National Science and Technology Forum. Furthermore, he regularly attended and participated in biennial conferences and supervised plant breeding students working on plant disease projects. 

Prof Herselman contributes to plant breeding in Southern Africa by training and mentoring the plant breeders of the future. “As a lecturer of fourth-year and honours Plant Breeding students, as well as supervisor and promoter of master’s and doctoral students, I am in the fortunate position to teach and mentor my students in one of the newest fields of plant breeding, namely marker-assisted plant breeding. All future plant breeders need this knowledge to make a success of their breeding programmes. Our students are the future plant breeders who will provide food to the nation,” she says. 

"As a plant pathologist, I am privileged to have been able to contribute to the quest for disease resistance in crop improvement and to have been recognised for it.” – Prof Zakkie Pretorius
The highest honour
Prof Pretorius view recognition by the industry – in this case, the plant breeding fraternity – as the highest honour for someone working in agricultural science. “As a plant pathologist, I am privileged to have been able to contribute to the quest for disease resistance in crop improvement and to have been recognised for it. I am also extremely grateful to colleagues and co-workers who have contributed over many years to the establishment of a productive and influential research group at the UFS,” he says.

Prof Herselman shares this sentiment. She says: “It means so much to me to know that I have made a difference and an impact on my students’ lives. It is a privilege to have the opportunity to work with under- and postgraduate students and to see them grow.”

She continues: “We strive to send out well-rounded students who can make a difference in the workplace and the community. This award means that I have succeeded in this goal, even though I do my work because I am passionate about it and not to receive recognition.”

Fight against fungal disease continues
Prof Pretorius continues to be involved in studies on host plant resistance and pathogenic variability. 

As a molecular plant breeder, Prof Herselman is pushing on with research focusing on the development of wheat lines with improved disease resistance. The work that she is doing makes a difference on both national and international level. “As part of my current research programme, we have made rust- and Fusarium head blight-resistant wheat lines available to South African breeding companies for use in their breeding programmes. The lines developed at the UFS will in a small way contribute towards the fight against fungal diseases in South Africa, thus securing the yield and livelihoods of farmers and consumers,” she says.

Her master’s and doctoral students who have completed their studies, also take the knowledge they gained at the UFS back to their countries and workplaces where they ultimately add value, especially contributing towards the fight against hunger. 

"“We strive to send out well-rounded students who can make a difference in the workplace and the community. This award means that I have succeeded in this goal, even though I do my work because I am passionate about it and not to receive recognition.” – Prof Liezel Herselman

News Archive

Research eradicates bacteria from avocado facility
2017-01-17

 Description: Listeria monocytogenes Tags: Listeria monocytogenes

Listeria monocytogenes as seen under an electron
microscope. The photo was taken with a transmission
electron microscope at the microscopy unit of the UFS.
Bacteriophages (lollipop-like structures) can be seen
next to the bacterial cells.
Photo: Supplied

“The aim of my project was to identify and characterise the contamination problem in an avocado-processing facility and then to find a solution,” said Dr Amy Strydom, postdoctoral fellow in the Department of Microbial Biochemical and Food Biotechnology at the University of the Free State (UFS).

Her PhD, “Control of Listeria monocytogenes in an Avocado-processing Facility”, aimed to identify and characterise the contamination problem in a facility where avocados were processed into guacamole. Dr Strydom completed her MSc in food science in 2009 at Stellenbosch University and this was the catalyst for her starting her PhD in microbiology in 2012 at the UFS. The research was conducted over a period of four years and she graduated in 2016. The research project was funded by the National Research Foundation.

The opportunity to work closely with the food industry further motivated Dr Strydom to conduct her research. The research has made a significant contribution to a food producer (avocado facility) that will sell products that are not contaminated with any pathogens. The public will then buy food that is safe for human consumption.


What is Listeria monocytogenes?

Listeria monocytogenes is a food-borne pathogenic bacterium. When a food product is contaminated with L. monocytogenes, it will not be altered in ways that are obvious to the consumer, such as taste and smell. When ingested, however, it can cause a wide range of illnesses in people with impaired immune systems. “Risk groups include newborn babies, the elderly, and people suffering from diseases that weaken their immune systems,” Dr Strydom said. The processing adjustments based on her findings resulted in decreased numbers of Listeria in the facility.

The bacteria can also survive and grow at refrigeration temperatures, making them dangerous food pathogens, organisms which can cause illnesses [in humans]. Dr Strydom worked closely with the facility and developed an in-house monitoring system by means of which the facility could test their products and the processing environment. She also evaluated bacteriophages as a biological control agent in the processing facility. Bacteriophages are viruses that can only infect specific strains of bacteria. Despite bacteriophage products specifically intended for the use of controlling L. monocytogenes being commercially available in the food industry, Dr Strydom found that only 26% of the L. monocytogenes population in the facility was destroyed by the ListexP100TM product. “I concluded that the genetic diversity of the bacteria in the facility was too high and that the bacteriophages could not be used as a control measure. However, there is much we do not understand about bacteriophages, and with a few adjustments, we might be able to use them in the food industry.”

Microbiological and molecular characterisation of L. monocytogenes

The bacteria were isolated and purified using basic microbiological culturing. Characterisation was done based on specific genes present in the bacterial genome. “I amplified these genes with polymerase chain reaction (PCR), using various primers targeting these specific genes,” Dr Strydom said. Some amplification results were analysed with a subsequent restriction digestion where the genes were cut in specific areas with enzymes to create fragments. The lengths of these fragments can be used to differentiate between strains. “I also compared the whole genomes of some of the bacterial strains.” The bacteriophages were then isolated from waste water samples at the facility using the isolated bacterial strains. “However, I was not able to isolate a bacteriophage that could infect the bacteria in the facility.

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