School of Agricultural, Earth and Environmental Sciences

Master’s Project Enhances Maize Improvement

Mr Malven Mushayi, a Senior Research Associate at Seed Co Ltd in Zimbabwe, has graduated with his MSc in Plant Breeding after investigating methods of widening the genetic base of the tropical maize germplasm to enhance maize improvement in Sub-Saharan Africa (SSA), completing his thesis in one year.

The low maize yield experienced in SSA hinders food security and economic development in a region dependent on maize production. Mushayi sought to develop high yielding hybrid cultivars to withstand current and future production constraints in tropical and sub-tropical environments, after systematic crosses with temperate maize germplasm. Hybrids developed between tropical and temperate maize germplasm had not been widely studied to improve tropical maize germplasm.

The narrow genetic base of tropical maize germplasm, caused by continuous directional selection by breeders, creates genetic “bottle-necks” which undermine breeding progress and limit achievable genetic gains. This can be circumvented by introgressing genes from temperate sources into the adapted tropical maize genetic base. Mushayi assessed genetic diversity levels and population structure among tropical and temperate maize germplasm lines to select unique genotypes. He determined heritability, genetic gains, and association between grain yield and yield components in maize hybrids derived from tropical and temperate maize inbred lines to devise a suitable breeding strategy. He also assessed grain yield stability and adaptability of these hybrids in five production sites in South Africa and Zimbabwe.

‘Development of hybrid cultivars with improved resistance or tolerance to biotic and abiotic stresses is of interest to ensure sustainable maize production amidst the climate change induced stresses experienced in SSA,’ said Mushayi.

Mushayi observed significant genetic distance between tropical and temperate maize germplasm lines, a key prerequisite for breeding. He demonstrated the utility of tropical and temperate maize germplasm in developing high yielding hybrids for specific maize production environments. He observed significant genetic variation and higher genetic gains, suggesting that the new tropical temperate derived maize hybrids have commercial value for breeding and the market place in Africa.

His experimental hybrids, which showed variable performance and yield stability, were selected for genetic advancement and commercialisation in the region. This could enhance future plant breeding progress and the attainment of high genetic gains, providing a guide on cultivar development and deployment to specific environments in South Africa and Zimbabwe and helping breeders to select ideal test locations to optimise genotype performance and efficiently use limited testing resources.

Mushayi recommended that plant breeders fully exploit the genetic diversity that exists between tropical and temperate maize germplasm to aid development of productive parental lines to use in developing productive hybrids for tropical and sub-tropical environments.

His research formed part of a larger Seed Co Ltd effort to introgress exotic genes into adapted local maize germplasm, enabling him to utilise Seed Co Ltd resources and establish field trials early and effectively.

Mushayi has been at Seed Co Ltd for more than 10 years. Pursuing his master’s research supported his work there, and equipped him with the skills, technical expertise, confidence and network he said will advance his plant breeding career.

By structuring his work, working hard, applying his plant breeding experience, and adhering to a strict research plan, Mushayi completed his master’s in one year. He credited the support and professional guidance of his supervisors at UKZN and Seed Co, Professor Hussein Shimelis and Professor John Derera, for making this possible. He thanked Seed Co Ltd for the financial support of his research, and thanked Dr Admire Shayanowako and Dr Isack Mathew at UKZN for their assistance.

Mushayi thanked Mrs Rowelda Donelly, Ms Marsha Manjoo and Ms Lyndre Anderson from UKZN for their administrative support, as well as the research staff at various sites used in the study for their technical assistance. Finally, he expressed gratitude to his wife, Beaullah Ruvimbo Magwenya, and child Mazvita, his parents, sisters, brothers, relatives and friends for their constant encouragement and support. He thanked God for giving him the ability, knowledge, strength and opportunity to undertake this study and perseverance to complete it.

Having completed his master’s, Mushayi looks forward to pursuing his PhD in the area of plant breeding to broaden his understanding of the field and enhancing the technical expertise and skills needed to run breeding programmes efficiently.

Words: Christine Cuénod

Photograph: Supplied