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Prof Willem Boshoff
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

Professor’s research part of major global programme
2011-04-04

 

Prof. Zakkie Pretorius, professor in Plant Pathology in the Department of Plant Sciences at our university

Research by Zakkie Pretorius, professor in Plant Pathology in the Department of Plant Sciences at our university, has become part of Phase II of a mayor global project to combat deadly strains of a wheat pathogen that poses a threat to global food security.

Prof. Pretorius focuses on the identification of resistance in wheat to the stem rust disease and will assist breeders and geneticists in the accurate phenotyping of international breeding lines and mapping populations. In addition, Prof. Pretorius will support scientists from Africa with critical skills development through training programmes. During Phase I, which ends in 2011, he was involved in pathogen surveillance in Southern Africa and South Asia.
 
The Department of International Development (DFID) in the United Kingdom and the Bill and Melinda Gates Foundation will invest $40 million over the next five years in the global project led by the Cornell University. The project is aimed at combating deadly strains of Ug99, an evolving wheat pathogen that is a dangerous threat to global food security, especially in the poorest nations. 
 
The Cornell University said in a statement, the grant made to the Durable Rust Resistance in Wheat (DRRW) project at Cornell will support efforts to identify new stem-rust resistant genes in wheat, improve surveillance, and multiply and distribute rust-resistant wheat seed to farmers and their families.
 
Researchers worldwide will be able to play an increasingly vital role in protecting wheat fields from dangerous new forms of stem rust, particularly in countries whose people can ill afford the economic impact of damage to this vital crop.
 
The Ug99 strain was discovered in Kenya in 1998, but are now also threatening major wheat-growing areas of Southern and Eastern Africa, the Central Asian Republics, the Caucasus, the Indian subcontinent, South America, Australia and North America.
 
Prof. Pretorius was responsible for the first description of this strain in 1999.
 
Among Cornell’s partners are national research centres in Kenya and Ethiopia, and scientists at two international agricultural research centres that focus on wheat, the Mexico-based International Maize and Wheat Improvement Center (known by its Spanish acronym as CIMMYT), and the International Center  for Agricultural Research in the Dry Areas (ICARDA), in Syria. Advanced research laboratories in the United States, Canada, China, Australia, Denmark and South Africa also collaborate on the project. The DRRW project now involves more than 20 leading universities and research institutes throughout the world, and scientists and farmers from more than 40 countries.


Media Release
28 March 2011
Issued by: Lacea Loader
Director: Strategic Communication
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: news@ufs.ac.za

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