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Rust diseases remain a serious threat to food crops in South Africa

07 August 2025 | Story Martinette Brits | Photo Stephen Collett

Prof Willem Boshoff shares insights from decades of rust disease research during his inaugural lecture at the University of the Free State.

Rust diseases of food crops remain one of agriculture’s most enduring and evolving challenges. In his inaugural lecture on 23 July 2025 at the University of the Free State (UFS), Prof Willem Boshoff shared how these complex pathogens continue to pose a significant threat to South Africa’s staple crops – and why continued research is more critical than ever.

Titled Battling rust diseases of food crops in South Africa, the lecture reflected on decades of rust research and recent developments in pathogen virulence. Prof Boshoff, from the Department of Plant Sciences, emphasised that the threat posed by rust fungi today stems from their “mechanisms of variability, their ease of long-distance spore dispersal, and subsequent foreign race incursions”.

A shifting disease landscape

Rust fungi are biotrophic organisms that cannot be cultured on artificial growth media. This makes rust research a technically demanding field that requires living pathogen collections, seed sources, skilled researchers, and specialised infrastructure. Prof Boshoff noted that for more than 35 years, the UFS has been at the forefront of this work, monitoring rust pathogens on wheat, barley, oats, maize, and sunflower.

While wheat remains the most extensively studied type, recent rust outbreaks across a range of crops point to a worrying trend. A localised outbreak of stem rust on spring wheat in the Western Cape has been linked to race BFGSF, which carries a previously unknown combination of virulence genes affecting both wheat and triticale. In 2021, leaf rust race CNPSK was detected, showing virulence to the highly effective Lr9 resistance gene.

More recently, stripe rust race 142E30A+ – first reported in Zimbabwe – was found in wheat cultivars from the Free State and northern irrigation areas. “Results revealed increased susceptibility of especially spring irrigation wheat cultivars,” Prof Boshoff explained, particularly due to its virulence to the Yr9 and Yr27 resistance genes.

Rust pathogens affecting other crops are also evolving. In maize, only a few lines with mostly stacked resistance gene combinations were effective against all tested isolates. In sunflower, just four of 30 Agricultural Research Council national trial hybrids showed resistance to local rust races.

Building better resistance

A key strategy in rust control lies in identifying and understanding resistance in host plants. This, Prof Boshoff stressed, requires optimised phenotyping systems for both greenhouse and field conditions, along with a solid understanding of available resistance sources. At the UFS, several recent studies have contributed valuable data to both local and international plant breeding programmes.

“Continued local and regional rust research is critical,” he said. “It supports early detection of new races, alerts to producers through updated cultivar responses, and enables efficient breeding strategies and other sustainable methods of rust management.”

The rust programme at the UFS has not only supported varietal release and on-farm risk management, but also strengthened collaboration between plant scientists, industry partners, and international researchers. With South Africa’s strategic location and history of rust surveillance, the programme continues to play a pivotal role in continental and global food security efforts.

About Prof Willem Boshoff

Prof Willem Boshoff is a plant pathologist with a strong background in wheat breeding and rust disease control. He holds four degrees from the University of the Free State, all awarded cum laude: a BScAgric (1994), BScAgric Honours (1995), MScAgric (1997), and PhDAgric (2001). His doctoral research focused on the control of foliar rusts in wheat.

Between 2001 and 2016, he worked as a wheat breeder and contributed to the release of several commercial cultivars. He joined the UFS Department of Plant Sciences in 2017 and has since been actively involved in national and international research projects, capacity development, and advancing disease resistance in food crops.

News Archive

Stem cell research and human cloning: legal and ethical focal points

2004-07-29

(Summary of the inaugural lecture of Prof Hennie Oosthuizen, from the Department of Criminal and Medical Law at the Faculty of Law of the University of the Free State.)

In the light of stem cell research, research on embryo’s and human cloning it will be fatal for legal advisors and researchers in South Africa to ignore the benefits that new bio-medical development, through research, contain for this country.

Legal advisors across the world have various views on stem cell research and human cloning. In the USA there is no legislation that regulates stem cell research but a number of States adopted legislation that approves stem cell research. The British Parlement gave permission for research on embryonic stem cells, but determined that it must be monitored closely and the European Union is of the opinion that it will open a door for race purification and commercial exploitation of human beings.

In South Africa the Bill on National Health makes provision for therapeutical and non therapeutical research. It also makes provision for therapeutical embryonical stem cell research on fetuses, which is not older than 14 days, as well as for therapeutical cloning under certain circumstances subject to the approval of the Minister. The Bill prohibits reproductive cloning.

Research on human embrio’s is a very controversial issue, here and in the rest of the world.

Researchers believe that the use of stem cell therapy could help to side-step the rejection of newly transplanted organs and tissue and if a bank for stem cell could be built, the shortage of organs for transplants would become something of the past. Stem cells could also be used for healing of Alzheimer’s, Parkinson’s and spinal injuries.

Sources from which stem cells are obtained could also lead to further ethical issues. Stem cells are harvested from mature human cells and embryonic stem cells. Another source to be utilised is to take egg cells from the ovaries of aborted fetuses. This will be morally unacceptable for those against abortions. Linking a financial incentive to that could become more of a controversial issue because the woman’s decision to abort could be influenced. The ideal would be to rather use human fetus tissue from spontaneous abortions or extra-uterine pregnancies than induced abortions.

The potential to obtain stem cells from the blood of the umbilical cord, bone-marrow and fetus tissue and for these cells to arrange themselves is known for quite some time. Blood from the umbilical cord contains many stem cells, which is the origin of the body’s immune and blood system. It is beneficial to bank the blood of a newborn baby’s umbilical cord. Through stem cell transplants the baby or another family member’s life could be saved from future illnesses such as anemia, leukemia and metabolic storing disabilities as well as certain generic immuno disabilities.

The possibility to withdraw stem cells from human embrio’s and to grow them is more useable because it has more treatment possibilities.

With the birth of Dolly the sheep, communities strongly expressed their concern about the possibility that a new cloning technique such as the replacement of the core of a cell will be used in human reproduction. Embryonic splitting and core replacement are two well known techniques that are associated with the cloning process.

I differentiate between reproductive cloning – to create a cloned human embryo with the aim to bring about a pregnancy of a child that is identical to another individual – and therapeutically cloning – to create a cloned human embryo for research purposes and for healing human illnesses.

Worldwide people are debating whether to proceed with therapeutical cloning. There are people for and against it. The biggest ethical objection against therapeutical cloning is the termination of the development of a potential human being.

Children born from cloning will differ from each other. Factors such as the uterus environment and the environment in which the child is growing up will play a role. Cloning create unique children that will grow up to be unique individuals, just like me and you that will develop into a person, just like you and me. If we understand this scientific fact, most arguments against human cloning will disappear.

Infertility can be treated through in vitro conception. This process does not work for everyone. For some cloning is a revolutionary treatment method because it is the only method that does not require patients to produce sperm and egg cells. The same arguments that were used against in vitro conception in the past are now being used against cloning. It is years later and in vitro cloning is generally applied and accepted by society. I am of the opinion that the same will happen with regard to human cloning.

There is an argument that cloning must be prohibited because it is unsafe. Distorted ideas in this regard were proven wrong. Are these distorted ideas justified to question the safety of cloning and the cloning process you may ask. The answer, according to me, is a definite no. Human cloning does have many advantages. That includes assistance with infertility, prevention of Down Syndrome and recovery from leukemia.

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