Maize can supply 50% of the caloric intake in sub-Saharan Africa but, in certain years, a farmer's entire crop can be wiped out. Now, scientists at the University of Cape Town, South Africa, along with colleagues at the South African seed company, Pannar, have developed a resistant variety of maize that they hope will help alleviate food shortages as well as promote the reputation of genetically engineered foods in Africa.
Dr. Dionne Shepherd of the University of Cape Town was to present the results of her recent work and that of coauthors B. Owor, R. Edema, A. Varsani, D.P. Martin, J.A. Thomson and E.P. Rybicki, at the annual meeting of the American Society of Plant Biologists in Chicago on July 8. in a symposium on Plant Biology in Sub-Saharan Africa.
Maize, which originated in Mexico, was carried to Africa in the 1500s and eventually displaced food crops such as sorghum and millet. Maize streak virus, an endemic pathogen of African grasses, was then carried to maize plants by viruliferous leafhoppers. African scientists have been working for more than a quarter century on developing resistant varieties of maize by selecting and crossing varieties with various degrees of resistance to the virus.
However, resistance requires multiple genes located on different chromosomes, so the process is not straightforward. The group at the University of Cape Town took the opposite approach. They mutated a viral gene that encodes a protein that the virus needs to replicate itself and inserted it into maize plants. When the virus infects one of these transgenic maize plants, the mutated protein, which is expressed at a high level, prevents the virus from replicating and killing the plant.
The transgenic maize variety has proven consistently resistant to MSV and the trait can be reliably passed on to the next generation and in crosses to other varieties. Trials are scheduled to begin soon, not only to test the effectiveness of the technology in the field, but also to ensure that the GE maize variety has no unintended effects on beneficial organisms that may feed on it. The resistant maize will also be tested to ensure that the viral protein is digestible and non-allergenic.
Scientists are hopeful that this year's field trials will demonstrate not only the effectiveness of this technology in producing resistance to a destructive pathogen but also the safety of GE foods. Part of the objective is to provide seed that will be sold at a minimal profit to
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