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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

UFS and Mexico forge links

2006-03-30

Some of the guests attending the signing of the memorandum of agreement were in front from the left Prof Wijnand Swart (Chairperson: Centre for Plant Health Management at the UFS), His Excellency Mauricio de Maria y Campos (Ambassador of Mexico in Southern Africa), Prof Magda Fourie (Vice-Rector: Academic Planning at the UFS) and Dr José Sergio Barrales Domínguez (Rector of the University of Chapingo in Mexico).
Photo: Stephen Collett

UFS and Mexico forge links
The Centre for Plant Health Management (CePHMa) in the Department of Plant Sciences at the University of the Free State (UFS) is presenting its first international conference. The conference started yesterday and will run until tomorrow (Friday 31 March 2006) on the Main Campus in Bloemfontein.

The conference is the first on cactus pear (or prickly pear) in South Africa since 1995. It coincides with 2006 being declared as International Year of Deserts and Desertification by the United Nations General Assembly.

During the opening session of the conference yesterday a memorandum of understanding (MOU) was signed between CePHMa and the University of Chapingo (Universidad Autonoma Chapingo) in Mexico. The signing ceremony was attended by the Ambassador of Mexico in Southern Africa, His Excellency Mauricio de Maria y Campos, the Rector of the University of Chapingo, Dr José Sergio Barrales Domínguez, and the Vice-Rector: Academic Planning of the UFS, Prof Magda Fourie, amongst other important dignitaries.

“South Africa and Mexico have a lot in common where agricultural practices in semi-arid areas and the role of the cactus pear are concerned,” said Prof Wijnand Swart, Chairperson of CePHMa at the opening of the conference.

He said that the MOU is the result of negotiations between CePHMa and the Ambassador of Mexico in Southern Africa over the past 12 months.

“The MOU facilitates the negotiation of international cooperative academic initiatives between the two institutions. This entails the exchange of students and staff members of the UFS, curriculum development, research and community service,” said Prof Swart.

“During the next two days, various areas of interest will be discussed. This includes perspectives from commercial cactus pear farmers in South Africa, the health management of cactus pear orchards, selection of new cultivars of cactus pear, and the nutritional and medicinal value of the crop,” said Prof Swart.

In his welcoming message Prof Swart explained that in recent years there has been increased interest in the cactus pear for the important role it can play in sustainable agricultural systems in marginal areas of the world. These plants have developed phenological and physiological adaptations to sustain their development in adverse environments.

“The cactus pear can serve as a life saving crop to both humans and animals living in marginal regions by providing a highly digestible source of energy, water, minerals and protein,” said Prof Swart.

“In an age when global warming and its negative impact on earth’s climate has become an everyday subject of discussion, the exploitation of salt and drought tolerant crops will undoubtedly have many socio-economic benefits to communities inhabiting semi-arid regions,” said Prof Swart.

“Plantations of cactus pear grown for fruit, forage and vegetable production, as well as for natural red dye produced from the cactus scale insect known as cochineal have, over the last two decades, been established in many countries in South America, Europe, Asia and Africa. The crop and its products have not only become important in international markets, but also in local markets across the globe,” said Prof Swart.

Detailed discussions on the implementation of the MOU will take place between CePHMa and the University of Chapingo after the conference.

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
30 March 2006

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