Plant Biology in Sub-Saharan Africa
Shepherd, Dionne , Owor, B. , Edema, R. , Varsani, A. , Martin, D.P. , Rybicki, E.P. , Thomson, J.A. .
Diversity of maize streak virus (MSV) and transgenic resistance to MSV in maize.
Maize streak virus (MSV) is a significant contributing cause of extremely low maize yields in Africa. Whereas a diverse range of MSV and MSV-like viruses is endemic in sub-Saharan Africa and its neighbouring islands, only a single reasonably genetically uniform group of variants, called MSV-A cause severe enough disease in maize to substantially influence yields. Towards designing effective strategies to control this variant, we report on a large survey that was conducted to assess the diversity, distribution and genetic characteristics of the Ugandan MSV-A population. This involved RFLP analysis of 389 MSV isolates, and sequence analysis of 68 complete MSV genomes. Importantly, we found that the most prevalent virus genotype identified in Uganda is a recombinant that is widely distributed throughout the surveyed regions. This indicates that recombination may be an important contributor to the emergence of MSV variants with both increased fitness and, possibly, novel pathogenic properties. We also report our development of transgene-derived resistance to MSV in maize. A mutated MSV replication-associated protein gene was used to transform Hi-II maize, which has shown stable expression to the 4th generation. Transgenic T2 and T3 generation Hi-II displayed a significant delay in symptom development, reduction in symptom severity, and higher survival rates than non-transgenics after MSV challenge, as did a transgenic hybrid made by crossing T2 Hi-II with the widely-grown commercial, highly MSV-susceptible white maize genotype WM3. This not only is the first maize to be developed with transgenic MSV-resistance, but is also the first all-African produced GM crop plant.
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1 - University of Cape Town, Department of Molecular and Cell Biology, Private Bag, Rondebosch, 7701, South Africa
2 - University of Cape Town, Department of Molecular and Cell Biology
3 - Makerere University, Department of Crop Science, Faculty of Agriculture
4 - University of Cape Town, Department of Molecular and Cell Biology, Electron Microscope Unit
5 - University of Cape Town, Department of Molecular and Cell Biology, Institute of Infectious Disease and Molecular Medicine
Presentation Type: ASPB Major Symposium
Location: International Ballroom/Hilton
Date: Sunday, July 8th, 2007
Time: 11:20 AM