FABI celebrated the successful completion of Mmatshepho Phasha’s PhD degree on 12 July making it an all-woman PhD record since the start of the year for the Institute. Mmatshepho presented her PhD Seminar entitled “Functional characterization of pathogenicity genes in Fusarium circinatum” with a small number of colleagues attending in person and a large audience ‘on line”. Her external examiners were Prof. Seogchan Kang, Pennsylvania State University, USA and Prof. Åke Olson of the Swedish University of Agricultural Sciences; Prof. Noëlani van den Berg was the internal examiner. As an introduction, Prof. Emma Steenkamp, as Mmatshepho’s primary supervisor (her co-Supervisors were Prof. Brenda Wingfield, Prof. Mike Wingfield and Prof. Martin Coetzee) praised Mmatshepo for the ground breaking work that she had conducted for her PhD.

The genus Fusarium includes some of the most destructive pathogens of agricultural and forestry crops.  Specifically Fusarium circinatum causes a severe disease on pine plants of all ages and is thus responsible for significant economic losses to forestry industries worldwide. Understanding the molecular mechanisms underlying the relationship between this pathogen and its host allows for a better options to control its spread and impact. Mmatshepho considered the roles of the putative pathogenicity genes RAS2 and FUB1 by generating RAS2 and FUB1 knockout mutants, and studying their phenotypes alongside a F. circinatum wild type strain. Transcriptomes of these mutants and the wild type strain were also sequenced, and gene expression patterns were compared. Results from the phenotypic studies showed that deletion of RAS2 caused reduced growth of F. circinatum colonies as well as reduced virulence of the fungus on Pinus patula seedlings. The results also showed that the lack of the RAS2 gene in the knockout mutant strain slowed conidial germination and resulted in fewer sexual structures being produced.

Results from analyses of gene expression patterns in the fub1 knockout mutant and the wild type strains also revealed a number of downregulated genes possibly involved in pathogenesis, and an upregulation genes of the bikaverin biosynthetic cluster. Collectively, the findings from this thesis showed that RAS2 and FUB1 are virulence factor genes in F. circinatum. The findings also suggest that the Ras2 protein is a master regulator that controls growth, development and virulence in this fungus, and that it does so in a MAPK-dependent manner. Much of the research has already been published in top scientific journals and contributes substantially to our knowledge of the molecular basis and mechanisms that fungi in general utilise to cause disease on their hosts.