Postdoctoral Fellow
I am a UP postdoctoral fellow in the Hans Merensky Chair in Avocado Research (previously the Avocado Research Programme), and have been a member of FABI since my Honours in 2016. My academic interest is focused mainly on the molecular aspects underlying plant-pathogen interactions.
I received my Master's degree in Microbiology in 2020, as a member of the same research group. My MSc. thesis was entitled "Identification and manual annotation of RxLR effector genes in Phytophthora cinnamomi".This research project was focused on identifying candidate RxLR effector genes from the P. cinnamomi genome, and specifically analysed those genes which were expressed during avocado infection. The results of this study highlighted several candidate RxLRs with putative virulence roles during infection of a susceptible avocado rootstock, paving the way for further research into these notable molecular weapons used by P. cinnamomi.
In 2025, I completed my PhD. project entitled "Investigating molecular mechanisms underlying avocado sunblotch disease". This study examined the molecular changes associated with avocado sunblotch viroid (ASBVd) infection in both asymptomatic and symptomatic trees using next-generation sequencing technologies. We explored how asymptomatic infections impact the host transcriptome, and correlated the production of viroid-derived small RNAs to the onset of leaf bleaching symptoms in symptomatic infections. This work highlighted the benefits of integrated high-throughput sequencing analysis for studying viroid-host interactions, and offered novel insights into disease caused by ASBVd and other members of the family Avsunviroidae.
Currently, I am working on a postdoctoral research project focused on exploring the functions of avocado resistance proteins, known as NLRs, in host defence against P. cinnamomi. This work aims to characterise avocado NLRs using a model host system in order to better understand the biological functions of these proteins in the P. cinnamomi-avocado interaction.
Conference Presentations
Joubert M., van den Berg N., Theron J., Swart V. From sequence to symptom — linking small RNAs to leaf bleaching in avocado sunblotch disease. Oral presentation at the 54th Congress of the Southern African Society for Plant Pathology; 18-21 January 2026, Umhlanga, South Africa.
Joubert M., van den Berg N., Theron J., Swart V. Avocado sunblotch viroid: the smallest avocado pathogen causing big changes in host gene expression. Poster presentation at the 12th International Congress of Plant Pathology; 20-25 August 2023, Lyon, France.
Joubert, M., van den Berg, N., Theron, J., and Swart, V. "Unravelling infection by Avocado Sunblotch Viroid". Poster presentation at the 52nd Congress of the Southern African Society for Plant Pathology; 1-3 August 2022, Pretoria, South Africa.
Joubert, M., and Van den Berg, N. "Discovery of Phytophthora cinnamomi RxLR effector genes expressed during Avocado infection". Poster presentation at the 51st Congress of the Southern African Society for Plant Pathology; 21-23 January 2019, Langebaan, South Africa.
Backer, R., Joubert, M., and Van den Berg, N. "Developing a novel pathosystem for the molecular study of Phytophthora cinnamomi using Nicotiana benthamiana". Poster presentation at the 4th Joint Congress of the South African Society for Bioinformatics and the South African Genetics Society; 20-23 September 2016, Durban, South Africa.
Joubert M, van den Berg N, Theron J, Swart V. (2026) Leaf bleaching is associated with extensive transcriptional reprogramming in avocado trees with sunblotch disease. Virology 10.1016/j.virol.2026.110903
Joubert M, van den Berg N, Theron J, Swart V. (2025) Small RNAs derived from avocado sunblotch viroid and their association with bleaching symptoms: implications for pathogenesis in avocado sunblotch disease. Archives of Virology 10.1007/s00705-025-06360-z
Joubert M, van den Berg N, Theron J, Swart V. (2024) Global transcriptomic analysis in avocado nursery trees reveals differential gene expression during asymptomatic infection by avocado sunblotch viroid (ASBVd). Virus Research 10.1016/j.virusres.2023.199263.
Joubert M, van den Berg N, Theron J, Swart V. (2022) Transcriptomics Advancement in the Complex Response of Plants to Viroid Infection. International Journal of Molecular Sciences 10.3390/ijms23147677
Joubert M, Backer R, Engelbrecht J, Van den Berg N. (2021) Expression of several Phytophthora cinnamomi putative RxLRs provides evidence for virulence roles in avocado. PLoS ONE 10.1371/journal.pone.0254645