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07 November 2019 | Story Leonie Bolleurs | Photo Johan Roux
Prof Zakkie Pretorius
Prof Zakkie Pretorius, Research Fellow at the UFS Department of Plant Sciences.
Prof Zakkie Pretorius, Research Fellow, and Prof Botma Visser, Associate Professor, both from the Department of Plant Sciences at the University of the Free State (UFS), partnered in a ground-breaking research project headed by Dr Melania Figueroa from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia. Together, these scientists solved a 20-year-old mystery, uncovering the origins of one of the world’s deadliest strains of cereal rust disease.

The manuscript, with the title, Emergence of the Ug99 lineage of the wheat stem rust pathogen through somatic hybridisation, was accepted for publication in Nature Communications.

According to a statement released by CSIRO, research shows that the devastating Ug99 strain of the wheat stem-rust fungus was not the result of a sexual cross between different rust strains as previously thought, but in fact was created when fungal strands simply fused to create a new hybrid strain.

This process is called somatic hybridisation and enables fungi to merge their cells and exchange genetic material without going through a complex sexual reproduction cycle. The study found that half of Ug99’s genetic material came from a strain that occurred in Southern Africa around 100 years ago and eventually spread to Australia.

The discovery implies that other crop-destroying rust strains could hybridise elsewhere with Ug99, for example, to exchange genetic material and create a whole new enemy.

While there was some speculation that rust strains could hybridise – based on laboratory studies in the 1960s as well as some earlier studies on the topic – this comprehensive research now provided the first genomic evidence that the process can generate new strains.

History of Ug99

Prof Pretorius was the first person to describe the dangerous Ug99 isolate, confirming the ability of the isolate to leave the Sr31 resistance gene ineffective (up to that time, effective against all known wheat stem-rust races). This laid the basis for international concern.

He named the field sample Ug99, based on the country of origin (Uganda) and year of sample collection (1999). 

“The Sr31 resistance gene and associated traits were so effective that the gene occurred in almost 70% of CIMMYT’s (Mexican-based International Maize and Wheat Improvement Center) spring wheat germplasm. In addition, many popular cultivars containing the gene were released around the world.”

“Ug99 then disappeared for a few years. When the race re-appeared in East Africa, it caused localised but severe epidemics,” he said.

Prof Pretorius continues: “Leading wheat breeders and pathologists were concerned that Ug99 could destroy wheat production in many global regions where wheat is critical for food security. Thus, in 2005, Dr Norman Borlaug, Nobel laureate and father of the green revolution, called for a meeting in Kenya where a global effort to combat the threat was initiated. The international wheat research community was mobilised and with funding primarily from the Bill and Melinda Gates Foundation and coordinated by Cornell University in the USA, research commenced.”

wheat stem rust

Wheat stem rust 14: Rust diseases are the cause of extensive crop losses each year. With this recent discovery, published in 
Nature Communications, scientists can now better identify the resistance genes which can be bred into wheat varieties to give crops 
long-lasting protection against rust. (Photo: Supplied) 

“From field trials in Kenya, it soon became apparent that 90% of the world’s wheat varieties were susceptible to Ug99. Although breeding and selection for resistance started in earnest, the pathogen adapted, gaining virulence for other previously effective resistance genes. At present, 13 races have been described within the Ug99 group occurring in 13 countries, mostly in Africa, but also in Yemen and Iran. Five of these races are present in South Africa, all confirmed by scientists from the UFS and ARC-Small Grain in Bethlehem. The original Ug99 has, however, never been detected in South Africa.”

Combined efforts

Rusts are common fungal diseases of plants. The spores of the fungus attach themselves to the stems and leaves of wheat plants and essentially suck the nutrients from the plant. Plants either die or produce shrivelled and low-quality grain. 

Group Leader at CSIRO, Dr Melania Figueroa, agrees that Ug99 is considered the most threatening of all rusts, as it has managed to overcome most stem rust-resistance genes used in wheat varieties.

“There is some good news, however; the better you know your enemy, the more equipped you are to fight against it. Knowing how these pathogens come about means we can better predict how they are likely to change in the future and better determine which resistance genes can be bred into wheat varieties to give long-lasting protection.”

Earlier this year, CSIRO worked with the University of Minnesota and the 2Blades Foundation to improve wheat resistance by stacking five resistance genes into the one wheat plant to combat wheat stem rust. 

The breakthrough came as Dr Figueroa’s group was sequencing Ug99 (then at the University of Minnesota), and at the same time a CSIRO team led by Dr Peter Dodds was sequencing Pgt21 in Australia (Pgt21 is a rust strain that was first seen in South Africa in the 1920s and believed to have been carried to Australia in the 1950s by wind currents). When the two groups compared results, they found that the two pathogens share an almost identical nucleus and therefore half of their DNA.

“This discovery will make it possible to develop better methods to screen for varieties with strong resistance to disease,” said Dr Figueroa.

Molecular fingerprinting

In addition to infection studies, molecular fingerprinting by members of the South African Ug99 race group led by Prof Botma Visser at the UFS, confirmed their genetic placement in context with Ug99 and other global stem rust races. The availability of the original Ug99 collection, along with other local rust isolates in long-term storage at the UFS, was essential to the success of the current research.

Despite the continued evolution of stem-rust variants, excellent progress has been made worldwide in the breeding of resistant wheat cultivars, including in South Africa. With funding from the Winter Cereal Trust, Dr Willem Boshoff, Senior Lecturer in the Department of Plant Sciences at the UFS, is responsible for the annual testing of all commercial wheat cultivars and advanced breeding lines for appropriate stem rust races.

Dr Melania Figueroa
Dr Melania Figueroa from the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Photo: Kate Langford

News Archive

SRC Inauguration speech: 22 January 2005
2005-01-22

Campus Head (Prof Peter Mbati). Dean of Students (Dr Natie Luyt). Deputy Director: Student Affairs and my boss (Mr. Teboho Manchu), Members of the University executive and Academic staff members, SRC members, Leaders of trade Unions and Student organizations, Distinguished guests, Ladies and gentlemen, most importantly first entering students and Parents receive my heartfelt revolutionary greetings.

Let me extend my word of appreciation to our distinguished guests for adding value and dignity to this event. Your presence here means a lot to us. Program Director what I bring here with me, assisted by facts, and is therefore just the work of my imagination. Like a love letter addressed to a sweetheart miles away, even though you do not know how she feels, what she wants to hear, and do not even know how her face looks like.

To me a speech is just an honest and intimate conversation. That is why I got into the habit of establishing a dialogue, or a debate, with my acquaintances looking at their faces and trying to persuade them of what I am telling them.

Mr. Speaker and Madam Deputy Speaker of the Student Parliament we are gathering at this ceremony, significantly few weeks after the release of grade 12 results, with the exception of those from Mpumalanga because of fraud. The Grade 12 results also show that only 18% of Black learners matriculated with exemptions, as compared to 53, 6% of white learners. This is an indication that our education system needs an overhaul.

We are also gathered here significantly a day after the management retreat held in Bloemfontein, Masselspoort. The retreat discussed, among other things, the transformation agenda, and some possible solutions to challenges we are facing now.

Most regrettably, we are gathered here when the whole world morns the victims of Tsunami tragedy. Let me therefore tore the line and convey our deepest condolences, from the last robot of my heart, to the affected families. Our hearts and thoughts will always be occupied by this horrified tragedy.

Creating a new Institution

I would submit, for purposes of debate and discussions that this Institution should strive to specialize and excel in regional rural development studies. Since our higher education, institutions in South Africa are generally weak in rural development studies. Instead, most of them tend to have an urban orientation to their programmes. Training everybody for the cities, big business and the private sector. This is a big weakness in a country with such large rural areas and population trapped in poverty, disease and ignorance.

Women’s studies

Program Director, it is only a moron who can argue against the fact that for us to reposition the institution around the regional development challenge, we need to start first with women empowerment. It is a fact that in most of our poor communities and families, it is women who withstand the worst of poverty. They are the ones who daily have to wipe tears from children who are hungry. It is women who look after the sick, the elderly, those dying from AIDS and the jobless. They are the one who have to fetch water, make fire and cook. There can therefore be no rural development studies without women studies, in particular on how to empower them and assist in the provision of basic services, so that they are relieved from some of the burdensome task of the society.

Registration Process

Mr. Speaker and Madam Deputy Speaker of the Student Parliament let me indicate that the registration is a process and not an event, so it cannot be concluded overnight. This huge process demands for people to stay calm, as there is no crisis. People should stop being excited. At the same time, no organization should use its cheap popularity and unilaterally disrupt the continuous and smooth running of the registration process at hand.

Let me strongly indicate, madam deputy speaker, that I am on record for stating that I have forgiven all those who have wronged us. I harbour no bitterness towards the protagonists of our painful and unfortunate events of the past week. And we will overcome this process not by our own devices but by the help of Almighty God and the grace of our Lord Jesus Christ.

Concerning registration of first years, we have programs, concerning that of senior students, we have programs, regarding graduations we have programs, and concerning HIV\AIDS we have programs. So, there is no need for people to press panicking buttons.

Mr. Speaker and Madam Deputy Speaker of the Student Parliament let me be opportunistic and welcome the entire student body on Campus for the academic year 2005. May our lovely first entering students have a happy and momentous year as part of Qwaqwa Campus of University of the Free State. May your studies be fruitful and enjoyable.

Student years are generally the happiest years of your life, so please make the most of them. While you are doing, all your preparations bear in mind that University is not an opportunity, it is just creating opportunities for a person.

On behalf of SRC members, our people, our students and management members I would like to welcome you all. Even though your parents are far away, here at Uniqwa you have more brothers, more sisters and more parents. Since we will love you with the same love as if we are from one family, and I have no doubts that management members will love and care for you as if you are their own children. Should you encounter any problem while studying at the Qwaqwa Campus of University of the Free State do not hesitate to contact us at the SRC offices because we need to ameliorate any factor influencing you negatively while on campus. I wish you well in the attainment of your academic pursuit.

Senior Students: We are not faced with just a new year but another academic year where we all have to work together to achieve our common goal of building our Institution through the development of human power. I urge you to invest your whole selves in this SRC.

For quite some time now, a debate has been ranging as to, whether has there been any progress in this incorporation process, or we are just moving with no direction. This debate is important, but I hasten to add not essential. The SRC is also involved in this debate, but with definite shift in emphasis. For us it is not important to participate in the debate than it is in finding solutions for the challenges of this new chapter in the history of humankind.

To my colleagues: Comrades, we are leading this Institution with a sense of pride and duty, and I know very well that we lead men and women, students who are determined to ensure that we all reach our destination safely and on time.

I said in one of our meetings that there are more enemies on our way, more than we can imagine. I think you witnessed that during the course of this week. The excitement and unnecessary confusions caused by some confused and loosed charlatans bear testimony to my statements. We should not reveal our game plans unless we are ready to slam.

Let me also borrow from the words of the late Albert Lethuli when he said and I quote: “There remains before us the building of the new land, from the ruins of the old narrow groups, a synthesis of the rich cultural strains which we have inherited. The task is immense”. Lastly, a navy divided within its ranks will be vanquished and destroyed by the enemy, but a navy united in purpose and action, loyalty and commitment will not drawn but sail on to victory.

In conclusion, let me call upon all political structures, church denominations, developmental structures, clubs, societies and forums to put aside all their differences, ideological insinuations and forge unity towards transforming Qwaqwa Campus of University of the Free State into an institution that is seen playing vigilant role in developing students academically, politically, socially, spiritually, religiously, culturally and otherwise.

Program Director, let me end my speech by indicating that every drop of my blood is telling me that Uniqwa is my home. I firstly became a student here, I became an activist here, I became a leader here, I became a president here, I will become a graduant here and hopefully I will become an employee here. So never, doubt my commitment towards the community of this campus.

Please be informed, in a central University of Technology’s way, that if there is no UNIQWA in HEAVEN, then I am not GOING.

Let us broaden the social base.

Tello Titus Wa-Motloung President General

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