PhD student (Crop Development) at the ARC Infruitec-Nietvoorbij, Graduation date: June 2021
Study leaders: Dr Cecilia Bester & Professor Elizabeth (Lizette) Joubert
"Investigating the effect of drought stress on honeybush will assist (plant) growers in improving their breeding programmes."
Focus on honeybush and drought stress
Honeybush occurs in a unique climatic envelope stretching from the Western Cape to the Eastern Cape. The environmental conditions in its natural distribution range are becoming drier and more extreme due to climate change. This leads to drought stress becoming one of the leading constraints for honeybush plant production and survival.
In my research, I focus on the metabolic and quality profiling of honeybush. Metabolic profiling involves analysing the specific response of honeybush to seasonal variation and drought stress by looking at its chemical and genetic responses to changing environmental conditions. I am looking at how seasonal changes affect the sensory quality of honeybush, its phenolic compounds, and how drought stress impacts on plant proteins (its proteomic profile). Phenolic compounds or polyphenols are chemical compounds produced by plants that humans benefit from (including antioxidants).
Why this matters
Honeybush has different sensory attributes and health benefits. The plant produces polyphenols (including antibiotic and antifungal compounds) to defend and protect itself from predators. To optimise the sensory attributes and health benefits of honeybush tea, we must make sure there are enough phenolic compounds produced by the plant.
At this stage, there are still many questions about the best time to harvest honeybush. Researchers are also still trying to understand how much and when to irrigate cultivated plantations.
By investigating the effect of the harvest season, climate and drought stress on the sensory profile and phenolic content, we can assist growers in improving their cultivation practices. Does honeybush harvested in summer taste better than honeybush harvested in winter? Is the antioxidant or phenolic content of tea harvested in summer higher or lower than tea harvested in winter? These are the kind of questions scientists are exploring.
In my work, I focus on two species, namely Cyclopia subternata and Cyclopia genistoides. This enables me to determine if there is genetic variation in the sensory profile and phenolic content of these species. The aim is to support the honeybush industry to identify species that are drought tolerant and suitable for quality tea production.
About the student
Mabizela, a recipient of the German Academic Exchange Service (NRF-DAAD) scholarship in 2018, is a PhD student in the Department of Horticulture at the Tshwane University of Technology (TUT). Her doctoral study, titled "Metabolic and quality profiling of Cyclopia subternata and C. genistoides in response to drought stress and seasonal variation", is set to be completed in 2020.
Mabizela obtained a master's degree in horticulture from TUT in May 2015 and published an article in the South African Journal of Botany on her results. She focused on the effect of growth media, plant growth regulators and the rooting potential of honeybush cuttings and the influence of genotype differences on them. Mabizela presented her research findings at eight local and two international conferences.
Gugu Mabizela, a doctoral student at the ARC Infruitec–Nietvoorbij, is investigating the impact of drought stress on the quality of honeybush tea.