Friday, March 25, 2011

Back to the Wild to Build Better, Climate-Resilient Wheat

Genetic archaeology may help save wheat from climate change

A genetic archaeologist of sorts, Cary Fowler works to save the wild species threatened by crop domestication.

Fowler is the executive director of the Global Crop Diversity Trust, an organization that seeks to preserve the genetic diversity of plants in seed banks. By providing a backup of wild varieties for their domesticated crop cousins, seed banks provide insurance in the case of a devastating blow to yields.

Given the losses in Russia and Australia in the past year that constricted global supply and generated conflicts over rising food prices, this insurance against climate uncertainty is critical. "Diversity equals options," said Fowler. "One of the things I know we're going to need is resilience. We're going to have to broaden the genetic base of our crops, because we're going to experience a lot of fluctuation."

Gene banks around the world hold tens of thousands of examples of wild wheat varieties. In the Middle East, Europe and China, where wheat is believed to originate, the number of wild varieties is countless.
Given wheat's importance in the global diet -- providing approximately 20 percent of the world's calories -- a resilient variety is essential. A 1-degree-Celsius increase in temperature correlates with a 10 percent decrease in overall crop yield, said Fowler.

For example, wild varieties could help control plant pollination to adapt to rising temperatures. Many domesticated plants pollinate in the middle of the day. If temperatures continue to rise as predicted, the heat could potentially sterilize the pollen.

But there are certain wild varieties of crops that pollinate in the wee hours of the morning, before sunrise. Less heat would give plants a significant head start to spread their seed.

Legacy from our ancestors -- limited diversity

"In the domestication process for agriculture, our Neolithic ancestors domesticated a rather small portion of wild plants that had around them," said Fowler. "Genetically speaking, that was a bottleneck. We went from having a lot of diversity to limited diversity."

This oversight from our well-intentioned ancestors is biting back now, he said, especially in the face of climate change.

"It's a big drag," said Susan McCouch, a professor of plant breeding and genetics at Cornell University who specializes in finding wild varieties of rice for breeding. "The wheat community has some constraints," compared to other crops.

The paring down of wheat's genetic diversity over generations is not easy to rebuild, but Mark Sorrells, another professor of plant breeding at Cornell, is optimistic: "It is possible to make [these] kind of broad generalizations ... but it is easy to cite examples in the other direction," he said, mentioning the durum wheat used for pasta. "Breeders have many tools to increase genetic diversity, and monetary resources are generally the limiting factor," rather than genetic potential.

Another major drag is a shortage of qualified breeders. The wild varieties are out there, said Fowler. The problem is there is no one going into the field to find them. Plant breeders, especially in the developing world, are scarce, and the time to develop new varieties is running out.

"We're systematically underinvesting," he said. "So we're at a stage now where we don't have the people power to make some of these changes."

When breeding for climate change-related stresses, hurdles center around the fact that plants' response to these stresses is controlled by many genes, said Peter Langridge, chief executive of the Australian Centre for Plant Functional Genomics, and those genetic changes may have different benefits depending on location -- drought in the United Kingdom is not the same as in Kazakhstan.

"The traditional approach is to carefully define the target environment and select for lines in the breeding program in these environments over several years," he said. "Today, we can be a bit more sophisticated." "A bit more sophisticated" turns out to be an understatement.

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