August 26, 2008
Carol Campbell,
SciDev.Net
African scientists have uncovered how one of the world's most
economically devastating crop diseases emerged, and hope to
genetically engineer disease resistant crops using the
information.
Researchers compared the genetic sequence of the virulent maize
streak virus (MSV) with ten less harmful strains of the virus
from across the continent, which infect other grass food crops
such as wheat and oats.
"We found that two relatively mild grass viruses had merged
through genetic recombination," says researcher Arvind Varsani,
from the University of Cape Town
(UCT), South Africa.
This merger resulted in an ancestral MSV far more potent than
its parents, which moved into maize before spreading rapidly
across the continent.
The researchers think that this occurred about a century ago,
just when commercial agriculture was replacing subsistence
farming and maize started to overshadow indigenous crops in
Africa.
The findings, published in the September issue of the
Journal of General
Virology, highlight the importance of research into plant
diseases.
"Our results mean that DNA viruses are evolving faster than was
thought. This rapid mutation increases the possibility of new
plant viruses emerging," Varsani told SciDev.Net.
"While plant diseases do not feature very highly in the public's
consciousness, their impact on food production causes more
suffering in the developing world than many high profile human
diseases," says lead researcher Darren Martin of South Africa's
Institute of Infectious Disease and Molecular Medicine.
Studying plant diseases can provide information about pathogens
that can be used to develop resistant crops.
Each year, at least two hundred samples of infected maize are
analysed by the UCT team. An analysis of virus-infected maize
from Burkina Faso, the Central African Republic, Ivory Coast,
Namibia and Zambia will begin this month and be placed in a
database.
Dionne Shepherd of the Department of Molecular and Cell Biology
at UCT is leading efforts to genetically engineer a type of
maize resistant to the streak virus.
"We have developed maize that is resistant to the streak virus.
Now we need to prove that it will hold up under different
conditions throughout sub-Saharan Africa," Shepherd told
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