Chocolate in Peril

Dec. 18, 2008— -- Is there any treat more decadent, more luxurious than chocolate? Well, it need not be a guilty pleasure - and not just because of growing evidence that eating the stuff can be good for you in some ways. Another reason to enjoy every delicious morsel this holiday is that the chocolate you eat was almost certainly grown on small farms in poor countries. When you buy chocolate, you help poor farmers feed their families. It's a start, at least.

The bad news for chocoholics is that the supply could start to run low. Chocolate is made from the fermented, roasted seeds of the cacao tree, whose scientific name is Theobroma, or "food of the gods". In recent years, demand has risen worldwide. Meanwhile, diseases destroy a third of the world's cacao crop every year, and that toll is set to get worse as they spread around the globe. What's more, cacao is a rainforest tree with shallow roots that hates drought, and droughts have hit harvests hard in recent years. Things could get worse as climate change gathers pace.

The good news is that help is at hand. Enter the scientists from Mars. Thanks to the biggest chocolate company in the world, Mars Inc., an unprecedented study of the cacao tree is now under way. Remarkably, the results are being made freely available. This is not pure generosity - you cannot sell chocolate if no one is growing it - but it could be good for everyone.

Supply can keep up with the world's growing chocolate hunger in two ways: by increasing the cacao-growing area or the yield of cacao per hectare. Since cacao is grown by poor people in poor countries - Africa grows 70 per cent of cacao, mostly in Ivory Coast and Ghana - there has been only sporadic investment in improving the trees. The cultivated strains are prone to drought and diseases, few farmers can afford fertiliser or pesticides to boost yields and what efforts there have been to breed better trees have been discouraging. "The yield of cacao has been flat for 30 years," says Howard Shapiro, head of plant science at Mars.

So the peasant farmers who dominate cacao production are expanding the area of cacao, mainly by slashing and burning patches of rainforest. This releases nutrients, on which the trees thrive for a time, after which the farmers move to a new patch. "This is contributing to deforestation," says Jim Gockowski of the International Institute for Tropical Agriculture's station in Accra, Ghana.

Higher-yielding strains could be the key to changing this. Strains that produce big crops in response to fertiliser could make it worthwhile for farmers to buy fertiliser, allowing them to grow more cacao on existing land. Such a switch to more intensive farming methods, the experts hope, would not only reduce pressure on the rainforests but also help small farmers to prosper.

Deforestation is not the only problem. Monocultures of cacao are very vulnerable to disease. Brazil's cacao plantations were gutted in the 1980s when witch's broom fungus was deliberately released amid local political disputes. Another even nastier fungus, frosty pod, destroyed plantations in Colombia and Costa Rica.

Neither witch's broom nor frosty pod have yet reached Africa or south-east Asia, but it is probably only a matter of time. "Those diseases will get out eventually," says Dennis Garrity, head of the World Agroforestry Centre in Nairobi, Kenya. Without resistant trees, Africa's biggest export crop could be devastated in as little as three years.This is why there is an urgent need for genetic studies. Lurking in the jungle may be wild trees that have already evolved resistance to some diseases, but where?

The oldest known use of cacao was in Central America, and the tree was long thought to have originated there. What's more, it was thought that there are only two or three main genetic varieties. Both ideas have been demolished by Juan-Carlos Motamayor of Mars's cacao research programme, who is based at the US Department of Agriculture's (USDA) research station in Miami, Florida.

His team analysed more than 1200 cacao samples collected by other researchers over the years. They used a form of DNA fingerprinting to identify the samples and study the trees' genetic relationships.

Their first finding was that nearly a quarter of the samples had been mislabelled. One reason, says David Kuhn, a molecular biologist working for the USDA in Miami, is that cacao seeds do not keep. Varieties are kept as clones grafted onto growing trees, which are harder to keep track of than seeds in a drawer.

Once the mislabelled samples were excluded, the researchers found the remaining samples could be divided into 10 genetically distinct groups, rather than three. The greatest diversity was from the upper Amazon, with the different groups corresponding roughly to the different tributaries of the river. This is strong evidence that cacao evolved here, rather than in Central America. It also suggests where disease-resistant genes might be found, especially as one genetic group comes from the same region as the frosty pod fungus.

Ending the confusion caused by mislabelling and identifying the unexpected diversity of existing collections is a huge step forward: breeders find themselves in possession of unexpected riches. This is just the start. In June, Mars, along with the USDA and computing giant IBM, announced an unprecedented public-private partnership to sequence the cacao genome. All the sequences will be made public: "Collective knowledge is better than cloistered knowledge, because more people will use it," says Shapiro. "This is a chance to secure our own future."

Meanwhile, the world's small but dedicated band of cacao scientists have begun searching for cacao trees with high yield, drought tolerance or disease resistance. Once these are identified, Kuhn's team will look for stretches of DNA that reveal which plants have these traits. This will greatly speed up breeding: rather than wait years for trees to grow, breeders can test new strains almost as soon as they are created to see if they have the markers for the desired traits.

"If we can treble the yield of cacao, farmers can tear up two-thirds of their lowest-yielding trees and use the land to grow fruit and timber as well," Shapiro says. Besides giving cacao the shade it likes, says Garrity, growing other tree crops alongside it will give farmers harvests year-round, and, he hopes, enough prosperity to abandon slash-and-burn for good. The use of nitrogen-fixing plants could reduce the need for fertiliser, while the mix of plants will reduce susceptibility to disease.

It isn't just about saving the planet. "Breeders can also use DNA markers to create new chocolate flavours," says Kuhn. And if speciality chocolate can also help peasant growers prosper, the effect could be just as sweet.