Mutation breeding for forage and grain tef
Growing up in rural Limpopo, South Africa, Patrick Rakau was struck by the common sight of goats eating plastic because there was limited vegetation.
“This experience motivated me to pursue a career in agricultural science, focusing on improving livestock nutrition,” he says. Another nudge in that direction was being raised by his late grandmother, who kept pigs, chickens and goats and had him helping with their care from an early age. This path has led Rakau to tackle a PhD in plant breeding at the African Centre for Crop Improvement (ACCI) based at the University of KwaZulu-Natal.
He started work on it in 2021 with a focus on the improvement of tef, and this research may result in more than two new varieties of this important forage crop being released in South Africa. Tef, which is native to Ethiopia, holds promise in other African countries because it grows well in dry, difficult conditions across a wide range of altitudes and is very nutritious for people and animals.
Before starting his PhD, Rakau completed a junior degree in Agricultural Management, an Honours degree in Pasture Science and an MSc in Pasture Science at the University of Limpopo. He switched to plant breeding after completing his MSc and joining the Agricultural Research Council (ARC) as a Junior Researcher. “I became interested in plant breeding while working with the ARC Cedara breeding team in 2016,” he says.
The title of Rakau’s research is “Response of Ethyl Methane Sulphonate-Mutagenized Tef [Eragrostis tef (Zucc.) Trotter] for Dual-Purpose Traits”. “I chose my research topic based on the need to develop improved forage cultivars to replace older cultivars with expired plant breeding rights (PBR),” he says. “At ARC, I identified three tef cultivars (Ivory, Highveld, and Emerson) with expired PBR and decided to use chemical mutation to induce genetic variation in these cultivars.”
His research began with the three parent tef cultivars being treated with different EMS dosages and soaking durations. The optimal dosage (2.11% EMS for 4 hours) was determined using the 50% lethal dose concentration (LD50). Next, the M1 and M2 generations, along with control (parent) cultivars, were evaluated in the field at Cedara Research Station.
Individual plants in the M3 generation were evaluated at Roodeplaat Research Station. Phenotypic variations in growth habit, flower shape, flowering and maturity stages, and panicle shape were observed. Selection was based on these traits, as well as grain and biomass yields and flowering behaviour. Segregation was visible. Selected mutant lines were multiplied and further evaluated in the field. The mutants displayed homogeneous traits with no visible segregation.
Elite tef genotypes derived from mutagenesis are presently being tested across six locations in South Africa (University of Limpopo Research Farm, Ermelo Agricultural Research Station, Cedara ARC Research Station, Roodeplaat ARC Research Station, Glen Agricultural Research Station, and Potchefstroom Agricultural Research Station). The selected genotypes provide valuable genetic resources for breeding and genetic improvement.
The project has had its ups and downs. An exciting aspect is the potential release of more than two new tef varieties by the end of the study. “These improved varieties are showing promising traits, such as reduced lodging and potential drought tolerance, making them valuable for future breeding and cultivation. Their development could contribute to enhancing the production and resilience in various growing conditions,” says Rakau.
On the downside, he has been challenged by the need to juggle professional and study work. While doing his research, he also led the National Department of Agriculture and Rural Development’s Cover Crop and Fodder Bank Project across eight provinces in South Africa: “This project involves basic research at six research stations and applied research at 40 farm sites. Balancing extensive travel, research activities, information days, and writing my thesis chapters has been particularly challenging,” he says.
Rakau is currently working simultaneously on his research and professional responsibilities. “I am collecting genotype-by-environment (G × E) data from six different locations, writing my thesis chapters, and preparing a peer-reviewed article for publication. Additionally, I am actively involved in the Cover Crop and Fodder Bank Project, which focuses on sustainable forage production across multiple provinces.” He hopes to graduate with his PhD in 2026.
Words: Shelagh McLoughlin
Photo: Supplied