A hearty congratulations to Phinda Magagula on becoming the second PhD student from the Avocado Research Programme (ARP) to successfully complete all requirements for their PhD degree in a week! Phinda presented his Prestige Seminar “Exploring the rhizosphere microbiome and potential management strategies against Dematophora necatrix” on Friday 7 March concluding a study of great importance to the domestic Avocado industry. Avocado is an important food crop with South Africa responsible for 11% of the world’s avocado production. The country has 2,024 ha planted to Avocado and produces 134,000 t of avocados per year, of which 45% is exported and the industry employs more than 155,000 people. 

Phinda’s PhD was completed under the supervision of Prof. Noëlani van den Berg, Dr Velushka Swart and Dr Arista Fourie. Professor Stanley Friedman (Volcani Center, Israel) and Dr Frédérique Reverchon (Institute of Ecology (INECOL), Mexico) were the external examiners for his thesis while Prof. Teresa Coutinho was the internal examiner.

Phinda was described by Prof. van den Berg as having a great work ethic and a hard worker as his research project required a lot of fieldwork and analysis and she congratulated him on finishing a “long and tough road”.

The discovery of the devastating white root rot (WRR) pathogen, Dematophora necatrix on Avocado trees in South Africa in 2016 was reason for concern to the local industry. Management of WRR currently relies on the removal of infected trees, as there are no commercially available rootstocks with tolerance or resistance to the pathogen and no chemical or biological control products registered for use on avocado in South Africa. Phinda’s study therefore aimed to evaluate potential management strategies for WRR in South African avocado orchards and to investigate the rhizosphere microbiome in the presence and absence of the pathogen to better understand its interactions with other microbes. He evaluated the efficacy of fluazinam (a fungicide) and EXTRASOL (a biological product) under field conditions over two growing seasons to manage D. necatrix and demonstrated that fluazinam either alone or in combination with EXTRASOL effectively controlled D. necatrix. This information is crucial for registering the fungicide to combat WRR.

The study further examined the rhizosphere microbiome diversity and composition of WRR-infected symptomatic, WRR-infected asymptomatic, and non-infected avocado trees across two commercial orchards. The rhizosphere microbiome study provides a basis for identifying potential biological control agents against D. necatrix from South African orchards. Understanding the rhizosphere of avocado plants is crucial for uncovering microbial interactions that influence soil health, disease suppression, and plant resilience. These findings provide valuable insights and open new opportunities, enabling the development of sustainable management strategies for WRR.