Out of Africa: the future of GM crops

By 2025, in sub-Saharan Africa, a region that embraces some of world's most impoverished nations, cereal yields will be little more than a tenth of those needed to sustain its burgeoning human population.

To feed the planet's projected nine billion people in 2050, current global food production must be doubled, without increasing the area of land under agriculture.

Africa's predicament is the most dire of any continent and is deteriorating, as eminent plant molecular geneticist Professor Jennifer Thomson made clear.

"Projected yields suggest sub-Saharan Africa will be 88.7 per cent short if they continue to use current farming technology," Thomson, from the Department of Molecular and Cell Biology at the University of Cape Town, said.

"Africa's population is projected to double by 2025, to 1.5 billion. If we want to feed Africa, we're going to have to use new technology."

In Australia recently for the ABIC 2006 conference, Thomson said up to 75 per cent of Africa's labour force was employed in agriculture and related industries. 70 per cent of Africans depend on agriculture as their sole source of income. Most are impoverished subsistence farmers who struggle to feed even their own families.

Growing crops is difficult enough, but post-harvest production losses to insect infestation, fungus diseases or rodents ranges up to 40 per cent in some years.

Plagued by insect pests and weeds, blighted by plant viruses, and desiccated by frequent drought, the continent has the lowest crop productivity in the world. Africa now imports 25 per cent of its grain requirements.

"Biotechnology is the tool needed to improve the efficiency, quality and productivity of farming in Africa, and to reduce costs and open new niche markets," Thomson said.

"[However], Africa is being denied some of these opportunities due to adverse influences. European nations are trying to prevent African countries making use of new crop improvement technologies."

Drought and famine

Africa is home to a range of viruses not found elsewhere, like cassava mosaic virus and maize streak virus. African farmers grow white maize, rather than the typical yellow varieties grown in the Americas, which are highly susceptible to streak virus.

During the 2004 drought and famine in Africa, a number of nations, including Zambia, Zimbabwe, Mozambique and Malawi, initially rejected shipments of unsegregated US maize, donated as food aid.

They claimed GM maize was potentially toxic, and if farmers planted any of the GM seeds it could compromise vital food exports to Europe, which rejected all GM produce.

Thomson said anti-GM NGOs, particularly those in Scandinavia, had joined with local anti-GM activists from Greenpeace, Friends of the Earth and Consumers International to block the maize shipments. Some had spread rumours that eating GM food would cause men to become sterile, she said.

"I wonder how people could do this -that any self-respecting person could put such ideas in African minds leaves me speechless."

All but two of the nations that initially rejected the unsegregated maize shipments subsequently relented; Zimbabwe and Zambia maintained their objections, but Zimbabwe ultimately accepted. However, authorities milled the maize before distribution to prevent farmers growing the seed. Thomson said the fact that maize streak virus would have devastated crops grown from the GM seed was ignored - no US variety is resistant to the disease.

The Zambian Government posted armed guards at locked village storehouses containing US maize, as desperate villagers grubbed for tubers of toxic plants to feed their starving children.

Yet most of the nations that rejected the unsegregated maize, including Zimbabwe and Zambia, had previously imported white GM maize from South Africa.

Genetic modification

The African farmer's plight could only be alleviated by cheaper fertilisers, increased use of intercropping, such as planting maize and legumes in double rows, integrated livestock-cropping systems, biological control of pests and, but most importantly, new crop technologies - including GM crops.

"If we could achieve biological control of mealybugs, perhaps by genetically modifying crops, it might result in a secure farm."

Thomson said her group at the University of Cape Town had developed a white maize variety that is completely resistant to streak virus in test plantings.

In the 1990s, Uganda had lost almost its entire cassava crop to African cassava mosaic virus. Researchers are in the early stages of developing a virus-resistant GM variety.

Thomson said witchweed was another huge problem for African farmers. Myriad seeds from the pretty, parasitic plant can lie dormant in a field for years, then germinate when maize or other cereal crops are planted, in response to chemical signals from the crops. Striga infestations have made it impossible to grow maize in parts of western Kenya.

She said pest-resistant Bt cotton varieties have transformed the cotton industry in South Africa. Most cotton farmers in South Africa now grow all or some Bt-cotton varieties.

The case for pest-resistant Bt maize, an unequivocal success in North America and some European nations, including Spain and Romania, is less clear.

Thomson said that, as in the US and Europe, the Bt transgene protects the growing crop against corn borers that damage the cobs allowing pathogenic fungi like Aspergillus to infect and contaminate damaged kernels with myxotoxins like fumonisins.

The problem in Africa is post-harvest damage. Farmers store a year's supply of corn in wicker cribs that are open to the sun, weather, infestation by beetle and weevil larvae, and mould contamination. Throat and liver cancers caused by fumonisins are rife in rural Africa.

Resurrection plants

Thomson's research group is trying to develop crops with enhanced drought tolerance, by screening for genes that allow Africa's so-called 'resurrection plants' to survive severe desiccation in harsh conditions.

She described a grass from South Africa's Zwa-Zulu Natal province that grows in rock crevices in the Drakensberg Mountains, where episodic rain provides a short-lived water supply.

Xerophyta viscosa enters dormancy after losing 95 per cent of the water from its tissues and all its chlorophyll. Within 72 hours of rain, it is green and flourishing again.

"The year we first collected it, the weather was very chilly, but two years later they'd had a drought, so the plants were subjected to day temperatures of 40 degrees, and overnight temperatures below zero.

"It rained 24 hours before we went climbing, and the day was misty with howling winds. It was below freezing when we got there, and these plants were now green.

Using a number of techniques, Thomson and her colleagues identified a number of genes that were 'hugely turned on' during desiccation - they coded variously for protective dehydrins, membrane proteins, transcription factors and osmoprotectants.

A tobacco plant experimentally endowed with one of the genes, XVSap1, was able to withstand 42-degree temperatures and high salinity under laboratory conditions.

The transgenic tobacco plants flourished, while control plants dried out and died. Drought tolerance is a complex trait, involving many genes, but Thomson said the experiment shows one gene can make a significant difference.

Other experimental GM plants in the international pipeline include phytoremediators that will sequester lead and cadmium from contaminated soil, a maize that resists corn rootworm, and "pharm" crops including varieties designed to express vaccine antigens.

'Golden rice' varieties enriched in pro-Vitamin A and iron, and 'golden' sorghum and cassava varieties, are also slated for introduction in Africa. But Thomson warned that transgenic crops would be no magic bullet for feeding the Third World. "We also need to improve infastructure, bring an end to wars and corruption, and educate women. If you want children to be properly fed, educate their mothers."

Priorities A meeting organised by United Nations Industrial Development Organisation (UNIDO) agriculturalists identified the biotechnology development priorities in Africa as: • Virus-resistant crops, such as maize with resistance to maize streak virus • Crops resistant to parasitic weeds, especially witchweed (Striga spp, Scrophulariaceae), which infests sorghum, maize, millet • Pest-resistant Bt maize varieties adapted to Africa • Decrease fungal infections that produce cancer-causing mycotoxins • More drought-tolerant crops.