Mary Ranketse celebrated the completion of her PhD journey at her Prestige Seminar “Genome sequences and molecular resources for Macadamia tree breeding in South Africa” on 10 March. Her PhD was completed under the expert supervision of Prof. Zander Myburg, Dr Rian Pierneef, Dr Charles Hefer (formerly of the ARC), and Prof. Gerda Fourie. Also present in the audience was Macadamias South Africa (SAMAC) Research & Development Manager, Dr Elrea Strydom.

The external examiners for her thesis were Dr Uljana Hess (University of the Western Cape) and Dr Stephanie Kerr  (Queensland University of Technology, Australia) while Prof. Fourie Joubert was the internal examiner.

Prof. Myburg congratulated Mary on completing her PhD and jokingly said that while Mary had “gone nuts” during her degree she was also the pioneer of the use of Oxford Nanopore Sequencing at the University of Pretoria. Her PhD project further added three new high quality and near-complete genomes for South African Macadamia cultivars which is of great value to the local industry.

Macadamia is the most expensive tree nut in the world and, while South Africa is the top producer worldwide, there is limited genomic resources available for Macadamias worldwide. Macadamia is unique amongst nuts in that it possesses a distinctive oil profile characterized by a notably high content of Omega-7 fatty acids in comparison to other tree nuts. Given that South Africa is the leading producer of the nuts globally, the local industry does not have any molecular tools for macadamia breeding and improvement.

Mary’s study explored the population structure of South African Macadamia cultivars using microsatellite markers and found high genetic diversity present within the population. Furthermore, genome sequencing, assembly and annotation was performed for the key cultivars: HAES 695/Beaumont, HAES 791, and Santa Anna. Finally, the underlying genetic mechanisms for fatty acid biosynthesis was elucidated in this study. This study led to the development of a microsatellite marker panel that provides genetic fingerprinting to the South African Macadamia industry for routine genotyping, clonal and parentage analysis of macadamia cultivars for production. The findings from this study contributes towards developing advanced molecular resources for precision macadamia nut breeding programs.