FABI celebrated the successful completion of Melissa Joubert’s PhD, with a Prestige Seminar on 23 May presented to a packed FABI Auditorium. Melissa first joined the Avocado Research Programme for an Honours degree in 2016. Her PhD supervisor, Dr Velushka Swart, and co-supervisors, Prof. Noëlani van den Berg (Chair of the Hans Merensky Chair in Avocado Research) and Prof. Jacques Theron (Department of Biochemistry, Genetics and Microbiology) praised Melissa for her tenacity and perseverance; and reflected on how she has grown and developed into a fantastic young scientist.

Melissa’s PhD examiners, Prof. Charith Adkar-Purushothama (Université de Sherbrooke, Canada), Prof. Andrew Geering (University of Queensland, Australia) and Dr David Read, were fulsome in their praise of her work, saying that she has contributed significant new knowledge regarding the mechanisms behind the pathogenicity of avocado sunblotch viroid (ASBVd) - a topic of research that has remained largely stagnant for the last 30 years.

Avocado is an important commercial crop in South Africa and will soon be the most exported tropical fruit globally. Avocado sunblotch disease is caused by ASBVd, a circular single-stranded RNA molecule only about 250 nucleotides in length. The disease is of global concern and is associated with lesions on the fruit, reducing its marketability, as well as reduced yield of infected trees. The disease can spread unnoticed without any visible symptoms in infected trees. Melissa’s study contributes in-depth knowledge of the ASBVd-avocado interaction, and is therefore an important starting point for further explorations into the molecular mechanisms underlying avocado sunblotch disease.