Final Report for LNC10-319
Perennial crops that live for many years increase sustainability by holding soil, reducing nutrient runoff, limiting pesticide use, and boosting farmer incomes through a decrease in inputs. All commonly grown grain crops are annuals, but we are working to develop intermediate wheatgrass (IWG), which has potential to become the first widely grown perennial grain crop.
This project will develop improved IWG plants and determine the effect of nitrogen fertility on sustained grain yield in IWG.
We are conducting a participatory plant breeding program that includes growing IWG on college campuses, on an NGO research station in Kansas, and at a commercial nursery in Wisconsin in order to identify superior genotypes. Through cross-pollination, we are combining several important traits that we have discovered: large seed, shortness, and shatter resistance. To answer the key question of the role of soil nitrogen (N) in sustained yield, a range of N addition treatments have been applied to IWG stands on three on-farm fields and at research stations in Kansas and Minnesota. Plant tissue nitrogen and seed yield traits are being measured.
Results from the proposed research will be published in peer-reviewed journals, reported to the scientific community through seminars, published in the popular press (web and hard copy), and presented to several hundred yearly visitors to The Land Institute.
Annual grain crops comprise a large and essential portion of the human diet, but the large-scale production of grains required to meet human food needs inevitably results in soil erosion, nutrient loss and subsequent contamination of waters, and pesticide contamination. Organic and no-till practices are among the most sustainable approaches to small grain production. However, organic systems depend on tillage for weed control and can experience soil loss through erosion and nitrogen loss through leaching into groundwater. No-till small grain systems require herbicides and often allow leaching of high levels of nitrogen into groundwater. Unfavorable weather and other uncontrollable factors often disrupt methodologies that rely on cover crops, rendering such approaches unreliable. As a perennial small grain crop, IWG would drastically reduce nitrogen loss by leaching, soil loss through erosion, and the need for tillage or herbicides for weed control. This potential comes at a time when farmers’ input costs are at an all-time high and nitrogen contamination of ground and surface waters is a serious issue facing society. Intermediate wheatgrass is an obvious choice for domestication because 1) a population is available that has already experienced a decade of selection for grain production by a joint Rodale Institute–USDA project, 2) it is widely adapted, and 3) cultural techniques have been developed in the forage-grass seed industry.
- The importance of sustainable grain production. In Kansas, 60% of gross farm income comes from the sale of grain crops (USDA-NASS, 1997). Globally, more than two-thirds of all cropland is dedicated to annual grain crops (FAO, 2003). Although land currently producing grains fed to livestock could be converted to pasture, annual crops grown for human consumption will remain important in the North Central Region and internationally. In 2004, wheat was planted on 29 million acres in the North Central Region, producing 1.1 billion bushels worth $3.7 billion (USDA-NASS, 2004). A sustainable supply of small grains is critical—the average American consumes about 83 kg of wheat per year (FAO, 2002).
- Soil Erosion. Although soil erosion has been recently reduced in the U.S., most of the improvement has come through taking land out of grain production rather than improving production practices. Conversion of highly erodable land to perennial cover (CRP) reduces soil erosion by an average of 17.2 tons acre-1 year-1, whereas better management of annual crops had only reduced erosion by 2.8 tons acre-1 year-1 between 1982 and 1992 (Uri, 2001). In other words, conversion to perennials is up to six times as effective at controlling erosion as is improved management of annual crops. Despite progress, soil erosion remains a major problem, causing the U.S. an estimated $37.6 billion in social costs annually (Uri, 2001).
- Chemical contamination. The most effective means of reducing erosion in grain production is no-tillage practices. Unfortunately, these practices depend heavily upon pesticides for weed and disease control. The pesticides that are required in order to reduce erosion from annual crop fields have potential to harm both humans and animals. Recent findings suggest that deformities and population declines of amphibians have been due to pesticide exposure (Sparling et al., 2001; Hayes et al., 2002). In humans, pesticides have been linked to profound learning disorders (Guillette et al., 1998), childhood leukemia (Reynolds et al., 2002), birth defects, shifts in sex ratios (Garry et al., 2002), and reduced sperm counts and quality (Swan et al., 2003). According to a study by the Centers for Disease Control and Prevention (CDC) of chemicals in 9,282 people across the U.S., at least one pesticide was detected in every person studied and the average person carries a mixture of 13 of the 23 pesticides analyzed (Schafer et al., 2004). Clearly, a non-chemical approach to reducing erosion in grain fields is needed, and perennial grain crops are an attractive solution.
- Nitrogen loss and contamination.Globally, only about 30-50% of applied nitrogen fertilizer is taken up by annual crops (Tilman et al., 2002). Due to the lack of year-round vegetative cover, annual cropping systems can lose five times the water and 35 times the nitrogen to leaching as perennial systems (Randall et al., 1997). Not only is lost nitrogen economically wasteful, nutrients lost from annual cropping systems can pollute ground and surface waters, endangering aquatic biodiversity thousands of kilometers distant (Burkhart and James, 1999; Turner and Rabalais, 2003). Some perennials can be fertilized at a rate of 200 kg N ha-1 yr-1 and lose only 1 kg N ha-1 yr-1 to leaching (Andrén et al., 1990; Paustian et al., 1990).
- The promise of perennial grains. The large number of funded SARE grants directed toward expanding use of perennial systems, such as pastures, is a testimony to the importance of perennials to sustainability. Perennial grain crops promise to bring the inherent sustainability of pasture systems (erosion control, nitrogen use efficiency, freedom from pesticides, and reduced input costs) into the millions of acres currently planted to annual grain crops in the North Central Region. Interest in perennial grains is growing due to the potential of large perennial root systems to sequester soil carbon for greenhouse gas mitigation. Furthermore, there is growing interest in using crop residues as biofuels, which could be achieved without exposing soil to erosion only if the grain crops are perennial.
We expect the proposed project to contribute to the following outcomes:
• Increased knowledge of how to grow and breed IWG for use as a perennial grain crop. Through experimentation and interaction with members of the community of practice, we have been improving our methodology for growing and breeding IWG. We expect this trend to continue, which will be evidenced by accelerated progress in the breeding program and improved techniques for growing the crop.
• Increased optimism for the potential of IWG as a crop in the food and agriculture community. Optimism is essential to achieving expanded research, development, and planting of the crop. This optimism will be derived from clear progress in the breeding program and the discovery of reliable techniques for raising a productive crop.
• Increased scientific research with IWG throughout the north central United States. For a new crop to succeed, a diverse team of researchers must be assembled to work on the challenges as they arise. Interest from scientists in many fields is growing, and we soon hope to have a wide array of scientific collaborators.
• IWG is planted on a large acreage for commercial use, which reduces soil erosion on sloping lands. This is an intermediate term outcome. Commercial plantings depend upon the development of improved varieties, agronomic practices, processing techniques, and marketable products. We expect that even with sustained research funding, this outcome is at least 10 years away.
Short-term outcomes will include increased knowledge of how to grow and breed IWG, optimism for its potential as a crop within the food and agriculture community, and an increased number of scientists actively engaged in IWG research.
Intermediate outcomes will include widespread planting of IWG by farmers and commercial use of the grain for food. To evaluate, we will measure indicators of progress toward these outcomes.
In the long term, we anticipate that diverse perennial grain cropping systems could replace more than 50% of current annual crop acreage. Success in breeding, growing, processing, and marketing IWG will serve as a proof of concept for perennial grains in general. IWG will spark interest in and funding for many other perennial grains, including wheat, rice, sunflowers, dry beans, maize and sorghum. Wherever perennial grain crops are planted, soil erosion will be reduced below replacement levels, nitrate loss to ground and surface waters will be reduced by more than 90%, and herbicide contamination will be sharply reduced. Furthermore, reduced input costs will benefit farmers and rural communities economically.
- On-farm experiments. Using three existing on-farm sites, we will establish replicated randomized experiments with a range of nitrogen applications each fall, from zero to 150 lb N per acre per year. Data on chlorophyll content, tissue N content, lodging, canopy temperature depression (an indicator of water stress), seed yield, and seed size will be collected each year. Additionally, input from collaborating farmers will be sought to obtain their insights into the results of the treatments. If they see other factors that may be responding importantly to the treatments, additional data will be collected. The treatments will also be applied on research stations in Kansas and Minnesota.
- Bulked mass selection for seed size and threshability. We have been using bulked mass selection to increase seed size and threshability, and we will continue this program. Each year we will sort the free-threshing seed out of all the seed harvested. These will be run through a robotic seed-weight sorting machine. The largest seed (less than 1% of the seed) will be planted in the field, the plants allowed to intermate the following summer, and the process will be repeated.
- Spaced-plant mass selection for seed size and yield.In this selection method, more than 20,000 individual IWG plants will be seeded in pots and transplanted into the field in the spring on 3-foot centers. By purchasing a mechanical transplanter, we will be able to increase the number of plants drastically from previous years, when only several thousand plants were used. Increasing the number of plants will allow us to dramatically increase the rate of progress from breeding. The widely spaced plants will be allowed to grow the first season. In the second summer, we will use visual selection to eliminate approximately 75% of the plants based on easily measured traits like growth-form and disease susceptibility. From each of approximately 5000 plants, 20 heads will be threshed and the seed weighed to determine seed yield per head. Hulls will be removed from all of the seeds using a mechanical rice huller that we will purchase for this purpose. Experiments in the last selection cycle demonstrated that seed size estimation is severely hindered by the presence on hulls on the seeds. After dehulling, 200 seeds will be counted and weighed from each plant to determine seed size. The best 50 plants will then be selected based on an index of seed yield per head and seed weight. These 50 plants will be dug up and placed in the greenhouse in the fall, and allowed to intermate. The crossed seed will be harvested and 20,000 plants again established in spring of the next year to start the cycle over. Using this method, a full cycle of selection requires only two years. Additionally, we will initiate a modest-scale breeding program for more northern locations, beginning with 1,000 spaced-plants in Wisconsin.
- Breeding to combine key traits: Over the past four years we have identified and studied three rare plant types: some with particularly short stalks (important for lodging resistance), some with very tough, shatter-proof heads, and some with particularly large seeds. Experiments have shown these traits to be simply inherited and dominant. We will seek to combine all of these traits into a single individual, with the hope of achieving a giant leap forward in harvested grain yield.
- Detailed Food Chemistry of the Grain: We will begin a characterization of the starch and functional properties of the grain. This preliminary analysis will indicate whether there may be some special high-value properties of the flour obtained from IWG.
- Student Participatory Evaluations: Three plants of each of 70 genotypes will be in collaboration with college students at campuses in Kansas, Iowa, and Arizona. In this manner, we will obtain robust estimates of the degree to which the traits we are breeding for are influenced by environment versus genetics. Furthermore, we will obtain the participation of a large number of individuals from diverse backgrounds in setting breeding objectives and considering ways to improve the methodology.
- Outreach activities. The on-campus research conducted in this project will function as an education and outreach activity. Students will be able to have hands-on interaction with this new perennial grain crop, and learn about the importance of plant breeding for sustainability.Plant breeders in general, and particularly those who are actively working to improve agricultural sustainability, are in short supply. We hope that this undergraduate research opportunity will entice some students to consider a career in perennial grain development. Articles about the ongoing IWG research will be written by members of the community of practice, targeted to regional publications, national farm magazines, food magazines, and scholarly journals. Some representatives of the community of practice travel extensively, giving about 40 presentations at institutions across the country per year—most of which will include discussion of IWG. More than 1000 visitors to The Land Institute receive tours annually, and IWG development will be presented to those visitors. Perhaps most importantly, we will continue to actively work to grow the community of practice by initiating collaborative projects with researchers and industry, as we have been for the past four years.
During the past three years we have conducted 1.5 breeding cycles in the main space-planted breeding program. We have expanded from evaluating 5,000 plants per cycle to 15,000 plants. Additionally, we have made controlled pollinations so that we have a detailed pedigree of every plant in the nursery. This helps us to make selections with greater accuracy.
Within the breeding program, it is difficult to evaluate progress because plants are grown every cycle in a different year and field. However, seed weight is relatively consistent across years and fields, so we have tracked it in each selection nursery. In these widely spaced nurseries, seed mass has more than doubled (see figure below).
More accurate evaluation of progress requires planting replicated, randomized experiments using remnant seed from each cycle of selection. We have planted such an experiment, and have documented a substantial increase in seed yield (see figure below). Biomass yield remains unchanged. Seed mass was much less improved than in the widely spaced nursery. Our hypothesis is that in dense plantings the plants that tiller and spread rapidly quickly dominate the field. Unfortunately, this plant type typically produces small seed. Varieties ultimately will need to be uniform for low vegetative spread in order to maintain large seed.
Bulked mass selection (selecting only the largest seed each generation) has increased seed mass at about the same rate as spaced-plant selection (see figure). Because bulked mass selection does not involve pollen control, progress is slowed by half. But because one cycle can be performed per year, (rather than a cycle every two years in spaced plant selection) progress has been equal. Interestingly, seed mass through bulked mass selection has happened mostly through early maturity, whereas in the main breeding program it has been through thicker stems and heads. We are now combining these two populations in hope of obtaining substantial increases in seed mass.
NITROGEN RESPONSE EXPERIMENTS
Trials with nitrogen fertilizer rates ranging from zero to 200 lbs/acre were established at four locations.
Yield of seed and biomass varied widely depending on the farm (presumably soil type) and moisture availability. In dry years, nitrogen fertilizer improved plant growth early in the season, but seed production was ultimately limited by moisture.
We conclude that in its current state, IWG may be more limited by soil moisture status than nitrogen availability. But to achieve maximum yields in good years, up to 100 lbs. of N per acre may be required. For maximum sustainability, this nitrogen should be provided in the form of manure or from fixation with intercropped legumes.
The students involved in the project had great enthusiasm and took the research well beyond where it was planned. In one year, the students evaluated the relationship between seed weight and relative growth rate. They found strong maternal control of growth rate in addition to seed size. In another year, they looked for twin seedlings in diverse genetic materials as a method to developing doubled haploids. They found that twin seedlings can appear at random independent of genotype. Both projects produced informative results. At one college, the research led to a grant proposal for an integrated multidisciplinary project studying the genetics of intermediate wheatgrass.
Starch analysis. Determination of the total starch content was performed by using an enzymatic approach. Starch was hydrolyzed to glucose using α-amylase and amyloglucosidase. Glucose was then measured by enzymatic oxidation forming gluconic acid and hydrogen peroxide which oxidizes p-hydroxybenzoic acid and 4-aminoantipyrine to a quinoneimine dye. Dye formation was monitored spectrophotometrically. Total starch content was determined to be 43.7 ± 0.9% (n=3), considerably lower than the starch contents in bread wheat (Triticum aestivum L.).
The determination of the amylopectin/amylose ratio was based on the formation of a complex between the lectin concanavalin A and amylopectin leading to a precipitation. Amylose and the precipitated amylopectin were separated and determined by enzymatic hydrolysis to glucose which was analyzed similar as described above. The amylose content was determined to be 22.95 ± 0.42% of the total starch content. Thus, the determined amylose/amylopectin ratio of ca. 23/77 is a common ratio for cereal grains.
Starch functionality was determined on the Rapid Visco Analyzer. The IWG had a much lower peak viscosity than did whole wheat pastry flour (1200 cps vs 3200 cps). This can be due to there being less starch in the flour as evidenced by the higher protein content in the IWG compared to the pastry flour. The lower peak viscosity indicates that it could be hard to have enough viscosity in a batter to hold gas during chemical leavening, and if one were to use IWG as the sold flour, it would probably be necessary to add a pregelatinized starch or gum to improve the baked volume.
Non-starch polysaccharides. Non starch polysaccharides were preparatively isolated using a heat stable α-amylase, amyloglucosidase, and the protease alcalase. Water insoluble non-starch polysaccharides were separated by centrifugation and water soluble non-starch polysaccharides were precipitated in 80% ethanol. Both ash and residual protein content in the soluble and insoluble non-starch polysaccharide preparations will be analyzed. The neutral monosaccharide composition of the non-starch polysaccharides will be determined by acid hydrolysis, followed by reduction and acetylation of the liberated neutral monosaccharides. The formed alditol acetates will be analyzed by GC-FID. Uronic acids will be measured enzymatically after acidic hydrolysis of the polysaccharides.
Hydroxycinnamic acids. The contents of ester-linked monomeric hydroxycinnamic acids, i.e. ferulic acid (trans/cis), p-coumaric acid, and sinapic acid, were analyzed by RP-HPLC-UV after alkaline hydrolysis of the flours. Alkaline hydrolysis was performed for 18 h at room temperature using 2 M NaOH. Liberated hydroxycinnamic acids were extracted from the acidified hydrolysate using liquid/liquid extraction with diethyl ether. The combined organic phases were dried, the residue was re-dissolved in methanol/water, and monomeric hydroxycinnamic acid contents were analyzed using HPLC: trans-ferulic acid, 910 ± 133 μg/g; cis-ferulic acid , identified, but below limit of quantification; trans-p-coumaric acid, 50 ± 13 μg/g; trans-sinapic acid, 140 ± 25 μg/g. The ferulic acid contents are higher than those usually found in bread wheat (roughly between 350 – 600 μg/g).
Ferulic acid dimers and trimers were analyzed by RP-HPLC-MS. Alkaline hydrolysis and extraction was performed as described for the hydroxycinnamic acid monomers. Separation and detection, however, was performed by HPLC-MS. The following amounts of ferulic acid dimers (dFA) and trimers (tFA) were determined: 8-8cyclic-dFA, 86 ± 0 μg/g; 8-8non-cylic-dFA, 17 ± 4 μg/g; 8-8tetrahydrofuran-dFA, 6 ± 1 μg/g; 8-5cyclic-dFA, 38 ± 2 μg/g; 8-5non-cyclic-dFA, 14 ± 3 μg/g; 8-5decarboxylated-dFA, not detected [sum 8-5-dFA, 52 μg/g]; 5-5-dFA, 29 ± 6 μg/g; 8-O-4-dFA 66 ± 5 μg/g; 5-5/8-O-4-tFA 5 ± 3 μg/g; 8-5non-cyclic/8-O-4-tFA, detected, but below limit of quantification; 8-5non-cyclic/5-5-tFA, detected, but below limit of quantification; 8-8cyclic/8-O-4-tFA, detected, but below limit of quantification, 8-O-4/8-O-4-tFA, not detectable. The diferulic acid contents are comparable to those found in bread wheat; however, the 22.9composition is very different. While 8-5-coupled dimers usually dominate in wheat (and in most other cereals) the 8-8-coupled dimers, especially the 8-8cyclic-dimer, are dominant in the intermediate wheat grass. Surprisingly, most of the trimers were found below the limit of quantification. This is somewhat unusual given the high amounts of monomeric ferulic acid attached to the intermediate wheat grass cell wall polymers.
Protein. The intermediate wheatgrass had much higher protein levels than what is typically found in wheat flour. Protein content was analyzed using a nitrogen analyzer following the Dumas AOAC method. Using a protein conversion factor of 5.7, the IWG averaged 17.55% protein, whereas wheat pastry flour was measured at 10.7% protein. For reference, all-purpose flour is typically around 10% protein, bread flour about 12% and whole-wheat flour around 14% protein. Gluten, gliadin and glutenin fractions were extracted from IWG using a series of solvent extractions with water-saturated butan-1-ol, NaCl and aqueous ethanol and aqueous propan-1-ol. Gluten was extracted from whole wheat flour and white all-purpose flour following the traditional hand wash method. Gliadin and glutenin fractions were also extracted from whole wheat flour and white all-purpose flour following the mentioned series of solvent extractions. Protein fractions were analyzed by SDS-poly acrylamide gel electrophoresis using hand-cast 13% acrylamide gels. Compared to whole and white wheat flours, the IWG lacked high molecular weight (HMW) glutenins, which are responsible for the elasticity of a dough system. IWG gluten had mostly α and γ gliadins and some low molecular weight (LMW) glutenins. Amino acid profiling of the IWG protein is underway, and results will be provided soon.
Baking tests. Standard AACC cookie, biscuit and bread baking tests were conducted with IWG being compared to equivalent flours for each product. For the cookie tests, IWG cookies had a similar spread but were slightly thicker, so the spread factor was lower than for all-purpose flour and whole wheat pastry flour. But structurally, IWG makes an acceptably shaped and set cookie. For biscuits, IWG had similar height and spread to whole wheat pastry flour and all-purpose flour. IWG performed very differently when making bread compared to whole wheat and white bread flour. For the same formula, the height in mm at the center of the loaf was 117 mm for bread flour, 50 mm for IWG and 65 mm for whole wheat flour. There was also much less of a crown formed. The gluten forming ability was also lacking, and it was almost impossible to sheet the dough with IWG as it would shred and not hold together.
Flavor Analysis. The flavor compounds in traditional yeast leaven bread made from whole grain hard wheat versus intermediate wheat grass (IWG) were characterized by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS) techniques. Immediately after baking, the crust was removed, frozen with liquid nitrogen, and ground with a mortar and pestle. The ground sample was subsequently extracted with 1 L dichloromethane [spiked with both 20 ppb of 2-methyl-3-heptanone (internal standard) and butylated hydroxytoluene (BHT)] for 15 hours under a blanket of argon gas, at room temperature under stirred agitation. The dichloromethane layer was removed, and another 1 L of dichloromethane was added, with stirred agitation under argon, for another 3 hours, and also removed. The combined extracts were dried over sodium sulfate and concentrated by vigreux distillation to 200ml, then fractionated by a high vacuum distillation (Solvent Assisted Flavor Evaporation – SAFE). The volatile isolate was concentrated by vigreux distillation to a final volume of 1 mL. Qualitative GCO analysis of the flavor isolate indicated differences in the intensity of the ‘key’ flavor compounds 2-acetyl-1-pyrroline, methional, 2-ethyl-3,5-dimethylpyrazine, furaneol, acetyl formoin, 2-acetyl-2-thiazoline and 2-phenylethanol (identified by GC-MS) between the IWG and hard wheat samples. The differences noted in flavor development in the IWG (in comparison to the wheat sample) provide a basis to design IWG products to have a more traditional flavor of wheat-based bread.
Conclusion. The data gathered so far revealed some key characteristics and challenges that need to be addressed in order to use IWG in food applications. Additional characterization is needed so that breeders can modify key traits to enhance the quality of IWG.
As a result of SARE-funded research with IWG over the past several years, two breeding programs to develop IWG for use as a perennial grain have been initiated at universities. Substantial increases in seed size, yield, and threshability that have been achieved through breeding have attracted attention from several food processors. Two companies have funded expanded planting of IWG in 2013, and are looking to expand onto farmers’ fields in 2014.
Economic analyses were not performed.
Ninety acres of intermediate wheatgrass were planted in fall 2013 on a research station in Minnesota. Seed produced at this location will be used by farmers to plant the first commercial grain production fields in fall 2014. We are working with a farmer group to arrange for this planting, but plans hinge on financial support from commercial partners. This progress has been made possible by the farmer collaboration supported by SARE (see photos below).
Educational & Outreach Activities
Current research with intermediate wheatgrass has been reported in peer reviewed journals and the popular press:
Larry Reichenberger. 2011. Forever Crop. The Furrow Sept.-Oct. 15-16.
David Van Tassel and Lee DeHaan. 2013. Wild plants to the Rescue. American Scientist 101:218-225.
Scott Bontz. 2012. Roots of Ages. Emperical Nov. 58-63.
Zhang, Xiaofei, Lee R. DeHaan, LeeAnn Higgins, Todd W. Markowski, Donald L. Wyse, and James A. Anderson. “New insights into high-molecular-weight glutenin subunits and sub-genomes of the perennial crop Thinopyrum intermedium (Triticeae).” Journal of Cereal Science (2014).
Turner, Margaret Kathryn, L. R. DeHaan, Yue Jin, and J. A. Anderson. “Wheatgrass–Wheat Partial Amphiploids as a Novel Source of Stem Rust and Fusarium Head Blight Resistance.” Crop Science 53, no. 5 (2013): 1994-2005.
Sievers, Savannah. “The Genetic versus Environmental Effects on Seed Yield Traits in Intermediate Wheatgrass (Thinopyrum intermedium).” Cantaurus 20 (2012): 47.
Hayes, R. C., M. T. Newell, L. R. DeHaan, K. M. Murphy, Simon Crane, M. R. Norton, L. J. Wade et al. “Perennial cereal crops: An initial evaluation of wheat derivatives.” Field Crops Research 133 (2012): 68-89.
Culman, Steve W., Sieglinde S. Snapp, Mary Ollenburger, Bruno Basso, and Lee R. DeHaan. “Soil and Water Quality Rapidly Responds to the Perennial Grain Kernza Wheatgrass.” Agronomy Journal 105, no. 3 (2013): 735-744.
Areas needing additional study
We have initated projects to study the economics of intermediate wheatgrass compared to corn and switchgrass. These results are needed prior to further expansion.
Breeding for increased seed size and yield continues to be the top priority in development of the crop as a perennial grain. Although breeding is dramatically increasing seed size, small seed continues to limit product development possibilities.
Additional study is required to develop suitable agronomic practices, particularly those that may involve intercropping with legumes to achieve a sustainable nitrogen source.