Honeybush research leads to PhD at TUT

17 August 2021


Dr Gugu Mabizela at work  in the laboratory.

For the past few years, South Africa's indigenous honeybush tea plants have been part and parcel of Dr Gugu Mabizela's life. Through her research she has found that Cyclopia plants that are harvested in summer produce the best quality tea. Her link with the species is set to continue now that Dr Mabizela has received her doctorate in Horticulture from the Tshwane University of Technology (TUT).

Dr Mabizela, who hails from Madadeni in Newcastle, received her doctorate at TUT's recent virtual graduation ceremony after completing her thesis "Metabolic and quality profiling of Cyclopia subternata and C. genistoides in response to seasonal variation and drought stress".

Honeybush has been her research topic since her MSc years at TUT. Dr Mabizela completed all of her postgraduate work while being part of the honeybush breeding programme at ARC Infruitec-Nietvoorbij in Stellenbosch since 2012, where she worked under the supervision of Agricultural Research Council (ARC) honeybush specialists Dr Cecilia Bester and Prof Lizette Joubert.

Her doctorate was funded through the DSI/ARC Honeybush Project, a three-year project funded by the Department of Science and Innovation and implemented by the ARC in support of the local indigenous honeybush industry. Since 2019 it has helped to greatly expand research and practical know how on the best practices available to further the growing of the local honeybush industry. It aims to strengthen the industry and its people, and to ensure that indigenous teas being produced in South Africa are ultimately of such a high standard that they can compete on the tea markets of the world.

Honeybush tea is produced from the plant leaves and stems of some of the 23 species of Cyclopia plants that grow naturally in South Africa's fynbos region of the Western and Eastern Cape. The tea is naturally caffeine free, is low in tannins and rich in antioxidants. These characteristics add to its status as a healthy beverage.

Ms Mabizela's PhD research formed part of an ongoing efforts to identify Cyclopia species that are particularly drought tolerant, but yet still produce quality tea. She focused on Cyclopia subternata and Cyclopia genistoides, and took particular note of how the former, which is a self-seeding plant, responds to seasonal variations and drought stress.

"It is generally accepted that the regions in which honeybush grow naturally are becoming drier and more extreme due to climate change. Drought stress can hamper plant production and survival – an increasing challenge to the fledgling industry," says one of her study leaders, Dr Cecilia Bester, one of the project leaders of the DSI/ARC Honeybush Project.

Dr Mabizela investigated the chemical and genetic responses to drought and seasonality by using methods such as high pressure liquid chromatography (HPLC), sensory analysis and proteomic analysis. This provided her with insights into how honeybush plants respond to different climatic conditions, and how it plays out in the phenolic content (such as beneficial antioxidant levels) and the sensory profile of the plants.

Based on the data, she identified that summer is the best season in which to harvest these species of honeybush, while also ensuring the best possible quality.

Dr Mabizela identified specific drought stress responsive proteins in Cyclopia subternata. She says that proteomic tools can be applied when trying to breed plants with a greater tolerance to water stress, and when identifying protein-encoding genes to be selected to generate plants that produce maximal yields.

"To optimise the sensory attributes and health benefits of honeybush tea, we must make sure that plants always produce enough phenolic compounds, without influencing the taste negatively," she says.

Dr Mabizela is thankful that her research is benefiting the honeybush industry. On a personal level, she is appreciative of the relationships she has formed throughout her years of study, and for the new skills she has acquired. "Patience tops my list of skills I've developed," she admits.
As a candidate research technician of the Western Cape Department of Agriculture since March 2021, she is now part of a research team that works on alternative crops. Her focus is still on improving the production of honeybush plant material, in terms of cultivation and an increase in the metabolic output of plants.

"In other words, I'm continuing where I left off with my PhD research," she adds proudly.

She has her sights set on becoming a well renowned researcher of honeybush and other Western Cape alternative crops.

"I feel there is still more to be done, especially on the crops that are still in their infancy in terms of research."

In 2020, another TUT student funded through the DSI/ARC Honeybush Project, Dr Jenifer Koen, also received her doctorate. Dr Koen took a close look at the characteristics of honeybush pollen, flowers and seeds, and ways to improve the propagation rates on a commercial scale.