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Wild Plants to the Rescue

Efforts to domesticate new, high-yield, perennial grain crops require patience and persistence—but such plants could transform agriculture

David Van Tassel, Lee DeHaan

The Art and Science of Domestication

2013-05VanTasselF2.jpgClick to Enlarge ImageSince 2000, when our current perennial-grain breeding programs began, the Land Institute has expanded, built new facilities and invested in new research technologies. Although we occasionally use DeHaan’s wooden contraption to lay out small plots, more often we use a mechanical transplanter, capable of planting in hours the number of plants we used to set in days spent on hands and knees. Although we can’t get a perfect grid with this technique, we use a GPS unit with centimeter-level precision to map the location of each plant in the field. These modest technological improvements, along with others, such as bar-code readers and handheld computers, allow us to study many more plants each season. In 2012, between our two domestication programs, we evaluated over 40,000 recently transplanted, individually spaced genotypes.

Plant breeding is always a numbers game. In our case it is even more so. The wild species we use are rich in genetic variation, and individual plants are highly heterozygous and do not breed true. In addition, we are looking for rare alleles, so the more plants we try, the better. These rarities may be new mutations, or they can be existing ones that are neutral—or are even selected against—in a wild population. A good example is mutations that disrupt seed dispersal, leaving the seeds on the heads long after they are ripe. An individual expressing this trait, known as shatter resistance, would have reduced fitness in the wild, but it is precisely the kind of plant we are looking for. Shatter resistance is an absolute requirement for a grain crop, because once grain falls to the ground it is virtually impossible for the farmer to recover it.

2013-05VanTasselFA.jpgClick to Enlarge ImageSidebar: Perennially Productive. Plant domestication has resulted in small, short-lived, high-yield annual crops and longer-lived, larger perennial crops. But smaller plants with the yield of annuals and the lifespan of perennials have not developed. The authors hope to fill this gap. For more, click the image at left.

Although we use each plant’s pedigree, along with sophisticated genetics software, to make predictions about the breeding value of each plant, our overall approach could be considered rather old fashioned, even “brute force.” It certainly feels like brute force, physically weeding, harvesting and threshing thousands of plants. Another downside of this strategy is that we produce tens of thousands of data points, but relatively little in the way of publishable results. Our work might be compared to that of a natural-products chemist who screens millions of microbes for novel antibiotics. But unlike the pharmaceutical industry, we do not have standard assays or product-pipeline benchmarks. Chemists know that antibiotics exist and that novel ones are periodically discovered. We have satisfied ourselves, through deductive reasoning and careful reading of the literature, that wild perennial herbs and shrubs can be domesticated to offer dramatically higher grain yield than their wild ancestors, but this has never actually been done.

In our efforts to produce at least one breakthrough on the scale of Alexander Fleming’s discovery of penicillin, we have reasoned that it is most important to push evolutionary change as fast as possible. When we have made more progress, perhaps we will find more opportunities for funding and collaboration, allowing us to analyze more carefully what exactly happened during the domestication process and describe how it could be repeated and, if possible, accelerated. That first breakthrough may come from a wild wheat relative.

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