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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

Fight against Ebola virus requires more research

2014-10-22

Dr Abdon Atangana
Photo: Ifa Tshishonge

Dr Abdon Atangana, a postdoctoral researcher in the Institute for Groundwater Studies at the University of the Free State (UFS), wrote an article related to the Ebola virus: Modelling the Ebola haemorrhagic fever with the beta-derivative: Deathly infection disease in West African countries.

“The filoviruses belong to a virus family named filoviridae. This virus can cause unembellished haemorrhagic fever in humans and nonhuman monkeys. In literature, only two members of this virus family have been mentioned, namely the Marburg virus and the Ebola virus. However, so far only five species of the Ebola virus have been identified, including: Ivory Coast, Sudan, Zaire, Reston and Bundibugyo.

“Among these families, the Ebola virus is the only member of the Zaire Ebola virus species and also the most dangerous, being responsible for the largest number of outbreaks.

“Ebola is an unusual, but fatal virus that causes bleeding inside and outside the body. As the virus spreads through the body, it damages the immune system and organs. Ultimately, it causes the blood-clotting levels in cells to drop. This leads to severe, uncontrollable bleeding.

Since all physical problems can be modelled via mathematical equation, Dr Atangana aimed in his research (the paper was published in BioMed Research International with impact factor 2.701) to analyse the spread of this deadly disease using mathematical equations. We shall propose a model underpinning the spread of this disease in a given Sub-Saharan African country,” he said.

The mathematical equations are used to predict the future behaviour of the disease, especially the spread of the disease among the targeted population. These mathematical equations are called differential equation and are only using the concept of rate of change over time.

However, there is several definitions for derivative, and the choice of the derivative used for such a model is very important, because the more accurate the model, the better results will be obtained. The classical derivative describes the change of rate, but it is an approximation of the real velocity of the object under study. The beta derivative is the modification of the classical derivative that takes into account the time scale and also has a new parameter that can be considered as the fractional order.

“I have used the beta derivative to model the spread of the fatal disease called Ebola, which has killed many people in the West African countries, including Nigeria, Sierra Leone, Guinea and Liberia, since December 2013,” he said.

The constructed mathematical equations were called Atangana’s Beta Ebola System of Equations (ABESE). “We did the investigation of the stable endemic points and presented the Eigen-Values using the Jacobian method. The homotopy decomposition method was used to solve the resulted system of equations. The convergence of the method was presented and some numerical simulations were done for different values of beta.

“The simulations showed that our model is more realistic for all betas less than 0.5. The model revealed that, if there were no recovery precaution for a given population in a West African country, the entire population of that country would all die in a very short period of time, even if the total number of the infected population is very small. In simple terms, the prediction revealed a fast spread of the virus among the targeted population. These results can be used to educate and inform people about the rapid spread of the deadly disease,” he said.

The spread of Ebola among people only occurs through direct contact with the blood or body fluids of a person after symptoms have developed. Body fluid that may contain the Ebola virus includes saliva, mucus, vomit, faeces, sweat, tears, breast milk, urine and semen. Entry points include the nose, mouth, eyes, open wounds, cuts and abrasions. Note should be taken that contact with objects contaminated by the virus, particularly needles and syringes, may also transmit the infection.

“Based on the predictions in this paper, we are calling on more research regarding this disease; in particular, we are calling on researchers to pay attention to finding an efficient cure or more effective prevention, to reduce the risk of contamination,” Dr Atangana said.

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