Genomic insights into the biology and evolution of Botryosphaeriaceae

Dissertation (MSc (Genetics))--University of Pretoria, 2019.

The Botryosphaeriaceae is a large family of fungi including many plant pathogenic species that cause diseases of important plants such as fruit trees, grapevine, eucalypts, pines and wheat. Members of this family are considered to be latent pathogens that infect their hosts without causing symptoms and often become pathogenic only after the plant host experiences environmental stress such as extreme temperatures, drought or physical damage. The aim of this study was to investigate the genetic factors influencing the infection and reproductive biology of the Botryosphaericeae and to develop molecular markers for future application in population genetic studies on these fungi. This was achieved by acquiring genome sequence data for species of prominent genera in the Botryosphaeriaceae and through the subsequent analyses of these data. Results showed that intact mating type genes exist in all Botryosphaeriaceae considered and that frequent, independent transitions from heterothallism to homothallism have occurred in this family. It was further shown that the Botryosphaeriaceae genomes contain high numbers and diversities of secreted hydrolytic enzymes and secondary metabolite biosynthetic gene clusters, which were correlated to genome size and the total number of predicted genes. Most importantly, they were also correlated with the host ranges of the species. A large number of highly transferable microsatellite markers were developed for the genera Lasiodiplodia and Neofusicoccum. These markers were capable of amplification in many species residing in these two genera and were shown to be able to distinguish a large number of multilocus genotypes from sample populations. Overall, this study has provided valuable insights into the biology and evolution of the Botryosphaeriaceae. It has also raised important questions that future research should consider.

Biochemistry, Genetics and Microbiology (BGM)

MSc (Genetics)

Unrestricted

Faculty of Natural and Agricultural Sciences