POLICYFORUM AGRICULTURE Increased Food and Ecosystem Perennial grains hold promise, especially for marginal landscapes or with limited resources Security via Perennial Grains where annual versions struggle. J. D. Glover, 1 * J. P. Reganold, 2 L. W. Bell, 3 J. Borevitz, 4 E. C. Brummer, 5 E. S. Buckler, 6 C. M. Cox, 1 T. S. Cox, 1 T. E. Crews, 7 S. W. Culman, 8 L. R. DeHaan, 1 D. Eriksson, 9 B. S. Gill, 10 J. Holland, 11 F. Hu, 12 B. S. Hulke, 13 A. M. H. Ibrahim, 14 W. Jackson,1 S. S. Jones, 15 S. C. Murray, 14 A. H. Paterson, 16 E. Ploschuk, 17 E. J. Sacks, 18 S. Snapp, 8 D. Tao, 12 D. L. Van Tassel, 1 L. J. Wade,19 D. L. Wyse, 20 Y. Xu 21 espite doubling of yields of major As highlighted in discussions of bio- part because of plant sterility and undesir- grain crops since the 1950s, more fuel production, perennial crops generally able agronomic characteristics ( 11). More Dthan one in seven people suffer have advantages over annuals in maintaining recently, programs have been initiated in from malnutrition ( 1). Global population is important ecosystem functions, particularly Argentina, Australia, China, India, Sweden, growing; demand for food, especially meat, on marginal landscapes or where resources and the United States to identify and improve, is increasing; much land most suitable for are limited ( 6) (fi g. S1). Perennial grain crops for use as grain crops, perennial species and annual crops is already in use; and produc- would have similar advantages and also pro- hybrid plant populations derived from annual tion of nonfood goods (e.g., biofuels) increas- duce food. Compared with annual counter- and perennial parents: rice, wheat (see the fi g- ingly competes with food production for land parts, perennial crops tend to have longer ure on page 1639), maize, sorghum, pigeon ( 2). The best lands have soils at low or mod- growing seasons and deeper rooting depths, peas, and oilseed crops from the sunfl ower, erate risk of degradation under annual grain and they intercept, retain, and utilize more flax, and mustard families ( 11– 16). Addi- 6 10 production but make up only 12.6% of global precipitation ( – ). Longer photosyn- tional plant taxa have potential to be devel- on July 11, 2010 land area (16.5 million km2) ( 3). Supporting thetic seasons resulting from earlier canopy oped as perennial grains ( 11). more than 50% of world population is another development and longer green leaf duration Plants may face physiological trade-offs 43.7 million km2 of marginal lands (33.5% of increase seasonal light interception effi cien- between seed productivity and longevity; global land area), at high risk of degradation cies, an important factor in plant productivity resources otherwise allocatable to seeds may under annual grain production but otherwise ( 7). Greater root mass reduces erosion risks instead be needed belowground to maintain capable of producing crops ( 3). Global food and maintains more soil carbon compared perenniality. However, this would not nec- security depends on annual grains—cereals, with annual crops ( 9). Annual grain crops can essarily prevent perennial grain crops from oilseeds, and legumes—planted on almost lose fi ve times as much water and 35 times as being high-yielding and economically viable, 70% of croplands, which combined sup- much nitrate as perennial crops ( 10). Peren- for at least two reasons. www.sciencemag.org ply a similar portion of human calories ( 4, nial crops require fewer passes of farm equip- First, crops are grown for unique character- 5). Annual grain production, though, often ment and less fertilizer and herbicide ( 9), istics, of which high potential yield is but one. compromises essential ecosystem services, important attributes in regions most needing For example, despite lower yield potential, pushing some beyond sustainable boundaries agricultural advancement. wheat is grown on more cropland than maize, ( 5). To ensure food and ecosystem security, in part because it can be grown in some envi- farmers need more options to produce grains Obstacles and Opportunities ronments for which maize is not well suited. under different, generally less favorable cir- Past efforts to develop perennial grain crops Similarly, lower-yield perennial crops could Downloaded from cumstances than those under which increases were limited by technologies and resources of be options where higher-yield annuals can- in food security were achieved this past cen- the time. Efforts in the former Soviet Union not reliably achieve full yields. In semiarid tury. Development of perennial versions of and the United States to develop peren- regions of sub-Saharan Africa, annual crops important grain crops could expand options. nial wheat in the 1960s were abandoned in often use less than 30% of rainfall owing to high rates of water draining below root 1The Land Institute, Salina, KS 67401, USA. 2Department of Crop and Soil Sciences, Washington State University, Pullman, zones, evaporation, and runoff, which partly WA 99164, USA. 3Sustainable Ecosystems–Agricultural Production Systems Research Unit, Commonwealth Scientifi c and explains the meager 1 metric ton/ha yields of Industrial Research Organization (Australia), Toowoomba, Queensland 4350, Australia. 4Department of Evolution and Ecol- annual grains common in such regions ( 8). ogy, University of Chicago, Chicago, IL 60637, USA. 5Institute of Plant Breeding, Genetics, and Genomics, University of Georgia, Athens, GA 30602, USA. 6U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) and Institute Perennial crops can reduce surface and sub- for Genomic Diversity, Cornell University, Ithaca, NY 14853, USA. 7Environmental Studies, Prescott College, Prescott, AZ surface water losses ( 8, 10) and be grown on 86301, USA. 8Kellogg Biological Station, Michigan State University, Hickory Corners, MI 49060, USA. 9Department of Plant highly erodible sites (fi g. S1). For example, 10 Breeding and Biotechnology, Swedish University of Agricultural Sciences, Alnarp, Sweden. Wheat Genetic and Genomic perennial types of pigeon peas, important Resources Center, Kansas State University, Manhattan, KS 66506, USA. 11USDA-ARS Plant Science Research Unit, North Car- olina State University, Raleigh, NC 27695, USA. 12Food Crops Research Institute, Yunnan Academy of Agricultural Sciences, food crops and sources of biologically fi xed Kunming 650205, China. 13USDA-ARS Sunfl ower Research Unit, Northern Crop Science Laboratory, Fargo, ND 58105, USA. nitrogen, are grown on steep slopes in regions 14Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843, USA. 15Department of Crop and of Malawi, China, and India ( 16). Soil Sciences, Washington State University, Mount Vernon, WA 98273, USA. 16Plant Genome Mapping Laboratory, Univer- sity of Georgia, Athens, GA 30602, USA. 17Cátedra de Cultivos Industriales, Facultad de Agronomía, Universidad de Buenos Second, because they intercept sunlight Aires, C1417DSE Buenos Aires, Argentina. 18Department of Crop Sciences, University of Illinois, Urbana, IL 61801, USA. over long periods of the year and their roots 19Charles Sturt University, E. H. Graham Centre for Agricultural Innovation, Wagga Wagga, New South Wales 2678, Austra- take up deep-soil water and nutrients, many 20 21 lia. Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108, USA. Global Maize Pro- perennials can sustain greater aboveground gram, International Maize and Wheat Improvement Center, Apartado 0660, Mexico DF, Mexico. production per unit land area than our most *Author for correspondence. E-mail: [email protected] widely grown annual crops on fertile land- 1638 25 JUNE 2010 VOL 328 SCIENCE www.sciencemag.org Published by AAAS POLICYFORUM Annual wheat versus perennial inter- funding from China’s National Natural Sci- mediate wheatgrass. Seasonal devel- ence Foundation. As happened during the opment of annual winter wheat (left of Green Revolution, private philanthropies can each panel) and its wild perennial rela- play key roles in supporting transformative tive, intermediate wheatgrass (right of each panel). Plant breeding programs plant breeding programs. are working to domesticate intermedi- Large investments have been committed ate wheatgrass (Thinopyrum interme- to developing technologies for biofuel con- dium) and to develop perennial wheat version of perennial crops because of their by crossing it with wheat ( 11, 13). ecological advantages over annual sources, despite their potential to displace food crops. and inexpensively, can facili- With similar commitments for developing tate the combining of desirable food-producing perennial grains, we estimate genes without the need for fi eld that commercially viable perennial grain evaluation over many years and crops could be available within 20 years. in every selection cycle. Natu- rally occurring genes that permit References and Notes 1. Food and Agricultural Organization of the United Nations exchange of DNA between chro- (FAO), The State of Food Insecurity in the World 2009 mosomes of different species or (Progress Report, FAO, Rome 2009). genera can be used to obtain off- 2. H. C. J. Godfray et al., Science 327, 812 (2010). spring with desirable traits from 3. H. Eswaran, F. Beinroth, P. Reich, Am. J. Altern. Agric. 14, 129 (1999). both parents ( 20). Plant breed- Fall Winter Spring Summer 4. C. Monfreda, N. Ramankutty, J. A. Foley, Global Biogeo- ers can use genetic modifica- chem. Cycles 22, GB1022 (2008). tion to introduce new genes, to 5. S. L. Pimm, The World According to Pimm (McGraw-Hill, 7 9 New York, 2001). scapes ( , ). For example, with no fertilizer modify existing genes, or to interfere with 6. D. Tilman et al., Science 325, 270 (2009). on July 11, 2010 inputs and without the benefi ts of centuries gene expression in specifi c cases. Classi- 7. F. G. Dohleman, S. P. Long, Plant Physiol. 150, 2104 of domestication, the perennial grass Miscan- cally trained plant breeders and agronomists (2009). 8. J. S. Wallace, Agric. Ecosyst. Environ. 82, 105 (2000). thus has 61% greater annual solar radiation will be needed to fully realize opportunities 9.