FABI celebrated the completion of the Institute’s 13th PhD candidate in 2019 with David Nsibo successfully defending his PhD on 21 November. His Prestige Seminar, entitled “Population genetics of the maize foliar pathogen Cecospora zeina in five countries of sub-Saharan Africa” was presented before a full auditorium.

David’s project was done under the supervision of Prof. Dave Berger of the Molecular Plant-Pathogen Interactions Research Group and Dr Irene Barnes. His external examiners were Prof. Stephen Goodwin (Purdue University, USA) and Prof. Eva Stukenbrock (Christian-Albrechts University of Kiel and Max Planck Institute of Evolutionary Biology, Germany) with FABI’s Prof. Brenda Wingfield the internal examiner.

Professor Berger praised David as a self-starter who has not let challenges in his project stop him from achieving his goals. David also spoke of his passion to learn and this has seen him already lecturing undergraduate classes. 

His PhD project focused on the fungal pathogen Cercospora zeina that causes gray leaf spot disease of maize, responsible for major yield losses in commercial and smallholder farms throughout sub-Saharan Africa. Using microsatellite markers, he determined the genetic diversity and population structure of 835 C. zeina isolates from Kenya, South Africa, Uganda, Zambia, and Zimbabwe, and established their evolutionary potential. Results revealed that C. zeina is highly diverse and structured, with migration and cryptic sexual recombination occurring among populations, although an attempt to induce the sexual stage was unsuccessful. Overall, C. zeina is genetically well-established in Africa with its population structure being influenced by sexual recombination, migration and human activities. This study, therefore, provides a basis for effective monitoring of C. zeina’s dispersal and is a tool for designing more effective regional-specific management strategies to reduce the acquisition and movement of highly virulent strains that overcome host resistance or fungicide control.