The Nature of Plant Viruses Expounded in Inaugural Lecture

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In his inaugural lecture, Professor Augustine Gubba of the Discipline of Plant Pathology in the School of Agricultural, Earth and Environmental Sciences (SAEES) gave insight into his research on the identification and characterisation of viruses infecting important food crops to devise effective and sustainable strategies to control and manage the diseases they cause.

Gubba dedicated his lecture to his parents, both educators, who instilled in him the value of education.

The lecture described his career from its beginnings at the University of Zimbabwe, where excellent instruction in the theory of the invisible microbes that affect plant growth during his Crop Science (Honours) degree fascinated him.

‘It will be clear that I have used viruses, specifically plant viruses, as the preferred mode of transport to traverse this journey,’ he said.

Gubba spent one year in Zimbabwe’s Agricultural Extension Service and eight years in the Department of Research and Specialist Services, attending his first international conference during that time, and contributing to an important project on cowpea viruses in Africa, moulding his career as a plant virologist.

Gubba explained the size and impact of viruses, amongst the smallest microbes and the most abundant biological entities which despite their minuscule size unleash havoc on their host cells, resulting in disease.

Familiar to most due to their role in causing sometimes debilitating human and animal disease, viruses also have devastating effects on crops grown for food and threaten food security. Symptoms of plant viruses include discolouration of leaves, stunted growth, and stem-pitting. Control strategies for these fast-mutating microorganisms include the removal of infected plants, the use of virus-free planting material, breeding for resistance, cross-protecting, or biotechnology-based methods.

He described maize lethal necrotic disease (MLND) and papaya ringspot virus (PRSV) to demonstrate the power of plant-infecting viruses, explaining how they reduced crop growth, vigour, quality, and marketability, leading to financial losses in control efforts.

A British Council Scholarship took Gubba to Wye College, University of London in the United Kingdom for his master’s degree after which he returned to his role in Zimbabwe and taught virology at his alma mater. In 1994 he was awarded a Rockefeller Foundation Scholarship to study for a PhD in plant pathology at Cornell University under the supervision of eminent plant virologist Dr Dennis Gonsalves.

In Gonsalves’ laboratory, Gubba worked on developing transgenic plants with virus resistance using the concept of pathogen-derived resistance, resulting in genetically modified organisms (GMOs).

He described this process and his PhD project on tomato-spotted wilt virus, where transgenic plants with resistance to the virus became an option to control the stubborn microorganism that results in enormous financial losses and has few alternative control strategies.

After completing his PhD, Gubba began a postdoctoral fellowship at Cornell University when he learnt of a plant virologist position at the then University of Natal which he took up in December 2000.

At UKZN, Gubba teaches three exit-level modules on viruses, plant virology, and biotechnology.

He has published over 60 research articles and holds a C-2 rating from the National Research Foundation. He received the Distinguished Teacher Award in the SAEES in 2014. His research expertise is recognised both locally and internationally where he serves on committees and technical teams, including the International Committee of Plant Virus Epidemiology, South African National Accreditation System, and the Southern African Society for Plant Pathology where he served as vice-president for four years. Gubba was appointed as a GMO Officer for the South African government and has given technical plant virology input to court cases as an expert witness.

In 2004 and 2005 he became involved with a project on PRSV in the Great Lakes region in southern Africa that led to a sabbatical in Hawaii, where the positive effects of GMO technology were evident.

Gubba drew attention to the achievements of some of the eight PhD and 15 master’s students he has supervised or co-supervised and described how they executed their research, its effectiveness, and the resulting publications. These included work on transgenic sweet potatoes and cucurbits, the effects of climate change on plant virology, the impacts of banana bunchy top virus, developing durable resistance to MLND for Kenya, and avocado sunblotch viroid.

This has resulted in contributions to the International Committee on Taxonomy of Viruses responsible for virus classification and the first reports of several viruses to the journal Plant Disease.

In 2022, Gubba spent nine months in the United States thanks to a Fulbright Fellowship where he focused on using CRISPR/Cas9 technology to edit sweet potato genes vulnerable to potyviruses - plants produced with this technology are not considered GMOs. He also worked on weed hosts of vegetable viruses.

Prospects for Gubba’s research will involve proactive work on evasive viruses using gene editing with CRISPR/Cas9 technology. He will also investigate artificial intelligence and fourth-generation technologies to predict outbreaks of insect viral vectors as a management tool for virus disease control.

Gubba acknowledged his students and their co-supervisors, PhD supervisor, colleagues, UKZN, and several funding organisations for their support and contributions. He thanked his extended family, and his wife, son, and daughter for their love and for keeping him grounded.

Words: Christine Cuénod

Photograph: Supplied