The Emergence of Perennial Wheat

http://www.motherearthnews.com//nature-and-environment/the-emergence-of-perennial-wheat-zbcz1403.aspx

wheat roots

I have recently written about wheat’s many excellent properties, both as a crop and as a food. (See the April-May and February-March issues of Mother Earth News and my blog posts on the “Great Gluten Panic” and wheat diseases.) Now it’s time to reverse field and mention wheat’s biggest deficiency: it’s an annual plant.

The world's natural landscapes are covered mostly by perennial plants growing in long-lived mixed stands, whereas more than two-thirds of global cropland is sown to monocultures of annual crops that require soil disturbance and re-sowing every year (with wheat prominent among the latter). The conversion from perennial to annual plant cover has dramatically altered the soil’s ecological health. Perennial plants are highly efficient and responsive micromanagers of soil, nutrients, and water, while annual crops such as wheat are not.

With shorter growing seasons and ephemeral, often small root systems, annuals provide less protection against soil erosion, waste water and nutrients, and store less carbon in the soil. In a field experiment in Missouri encompassing 100 years of data collection, perennial crops were more than fifty times more effective than annual crops in maintaining topsoil.

So-called “no-till” methods (in which annual crops are farmed with little or no tillage) reduce soil loss but require heavy chemical inputs and can actually increase nitrate pollution of water resources. (Nitrogen losses from annual crops may be 30 to 50 times higher than those from perennial crops.) Meanwhile, organic farming with wheat or other annuals addresses the problem of chemical contamination, but usually requires as much or more soil-wrecking tillage than does conventional agriculture. And the inadequate root systems of annual species handle water and nutrients inefficiently even when crops are grown organically.

Given these problems, interest in breeding a perennial version of wheat is once again on the rise. Hybrids between wheat and related grass species, once sown, can re-emerge each season without further sowing, as do pasture grasses. The idea dates back to the early twentieth century, when breeders found that they could do in their nurseries something that nature had done many times during the evolution of wheat and its many relatives: hybridize different species and double the chromosome number of the hybrid to produce what is in effect a new, fertile species.

This is a process similar to the one through which the highly successful feed- and food-grain called triticale was developed. But triticale, like its parents durum wheat and rye, is annual and must start from seed each year. In contrast, hybridization of an annual wheat variety with perennial grasses belonging to the related genus Thinopyrum (no GMOs needed!) can produce perennial plants. They have wheat's grain-producing ability along with the perenniality that's characteristic of Thinopyrum. And growing perennial wheat would help reduce soil erosion, maintain soil cover, and cut back on fossil-fuel and chemical inputs.

A few perennial wheats were developed in the past, including a grain-forage type called ‘MT-2’ released by Montana State University in the 1980s. Washington State University has worked on perennial wheat since the 1990s, as has The Land Institute in Salina, Kansas (TLI, where I work as a perennial sorghum breeder) since 2001. But perennial wheats developed to date have had problems with sparse seed-set, low productivity, and spotty post-harvest survival. Populations currently in experimental plots are much better than the older ones but still not farm-ready, and more breeding will be required. TLI's perennial wheat breeder/geneticist, Shuwen Wang, says his goal is to identify perennial plants that have the right balance between numbers of chromosomes from the annual and perennial parents, then interpollinate such plants and select perennial, genetically stable plants with better seed production. Stay tuned.

Stan Cox is a senior scientist at The Land Institute in Salina, Kansas, and author most recently of Any Way You Slice It: The Past, Present, and Future of Rationing (The New Press, 2013).