By Carolyn King
Perennial grain crops offer some intriguing benefits for Prairie growers, such as fewer inputs, but first breeders have to develop commercially viable perennial grains.
By Carolyn King
Perennial grain crops offer some intriguing benefits for Prairie growers. For instance, once established, perennials tend to require fewer inputs than annuals. They are better able to make use of moisture and fertility resources during the entire growing season, including early spring and fall. They provide good protection for the soil throughout the year. And perennial grains offer a way to produce food crops on fields that are marginal for annual crop production.
But first breeders have to develop commercially viable perennial grains.
That’s a significant challenge. Some of our annual grain crops have gone through thousands of years of selection by farmers and breeders to transform wild plants into the elite varieties grown on the Prairies these days. Even with today’s breeding techniques, this transformation still requires decades.
A handful of crop breeders around the world are taking on this challenge. One of those is Dr. Douglas Cattani, who heads the perennial grain breeding program at the University of Manitoba. This program has received funding from Growing Forward 1, Manitoba’s Agri-Food Research and Development Initiative, the University of Manitoba and the Western Grains Research Foundation.
Cattani’s program is not yet three years old. So far, its main focus is on intermediate wheatgrass, as a cereal crop, and perennial sunflower, as an oilseed crop.
Wheatgrass for grain
Some Prairie farmers are already familiar with intermediate wheatgrass (Thinopyrum intermedium) as a forage crop. “Intermediate wheatgrass has been grown in North America and around the world as a forage grass for years,” says Cattani. It is a winter-hardy, drought-tolerant grass that lasts about six years under Manitoba conditions. The species was originally introduced to North America from Russia.
He notes, “There have been programs to improve intermediate wheatgrass [as a forage species] especially over the last 50 years, and some ongoing work to convert it to a grain-producing plant since the mid-1980s.” For instance, The Land Institute, a Kansas-based, non-profit research and education organization, has an intermediate wheatgrass breeding program. It is currently developing lines suited to central Kansas and refers to the crop as Kernza.
The first stage in Cattani’s intermediate wheatgrass program is to evaluate a wide range of germplasm. “Our biggest concern has been adaptation for Manitoba conditions. We need something that will survive and produce relatively uniformly year after year. So we’re looking at initially survival, and secondly – and as importantly – yield.”
Cattani has obtained intermediate wheatgrass germplasm from The Land Institute and from around the world through the USDA’s Germplasm Resources Information Network. The materials have been through two Manitoba winters so far. He says, “We have been trying all of those materials. Some of them are really bad and some are decent.”
Just because an intermediate wheatgrass line performs one way in another region does not guarantee it will perform the same way in Manitoba. Cattani gives an example: “We’ve tested materials selected in Kansas for dwarf characteristics because shorter plants have an increased harvest index [ratio of grain yield to above-ground biomass at maturity], which is very important for improving yield. When we grow the Kansas dwarf lines here, we find differences in plant height of up to 90 centimetres. Part of the reason for that may be the difference in hours of sunlight. The maximum day length in Kansas is about 14.5 hours of light, whereas in Manitoba our longest day is about 16 hours 20 minutes. So we may be seeing the effects of the interaction of the environment with the genetics.”
In addition, the Manitoba researchers are selecting intermediate wheatgrass materials for several other traits. For instance, they are looking for non-shattering seed heads, so the seeds don’t end up on the ground, and for threshability, so the hulls come off the grain easily. They’ll be looking at grain quality once they make some initial selections.
As well, the researchers are starting to work on selecting lines that emerge quickly and vigorously. Surprisingly, early emergence seems to be connected to smaller seed size. “We’re looking at some materials that have a big range in seed size – some of the seeds are about 50 per cent larger than others. Our first tests in both the lab and the field found that the smallest seeds emerge faster or as fast as anything else,” notes Cattani. “Those results are based on a uniform depth of planting, so it’s not that the smaller seeds were seeded shallower.”
Cattani’s researchers also are keeping an eye out for disease and insect issues in their intermediate wheatgrass materials. At present, if they see any diseased plants, they immediately remove those materials from the breeding program. Once the researchers have developed some good lines, they’ll evaluate disease resistance in those lines in a more formal way. They haven’t had any insect problems in their plots so far, although Cattani expects they might encounter pests such as cutworms that occasionally affect perennial grass seed crops in Manitoba.
“Manitoba has several native perennial sunflower species, and the one we are most interested in is the Maximilian sunflower (Helianthus maximiliani). In Western Canada, we have a lot of this perennial sunflower growing along roads and ditches,” says Cattani.
The Manitoba researchers are currently evaluating wild perennial sunflower material from Manitoba and material from other perennial sunflower breeders. They are also crossing wild Manitoba materials with lines developed by the Land Institute. The researchers hope to eventually develop lines suited to Manitoba that have such traits as higher yield potential and plants with a single large flower.
Having one big flower is a key characteristic for commercial production. “In nature most sunflowers have multiple heads on the plant,” explains Cattani. “However, if you have a sequence of flowers blooming over a month and a half period, by the time the last ones have flowered and set seed, the first ones have long since dropped their seed. With a single head, you have uniformity in harvest time.”
Some U.S. breeders have developed uniflower Maximilian lines, but those lines aren’t suited to Manitoba. “Some of the materials we have collected in Manitoba flower in the first couple of weeks of July. In contrast, native sunflowers that other breeders have worked with, especially in the southern U.S., are short-day plants, flowering in September through October, for harvesting around Nov. 1,” says Cattani. “If we planted those materials here, they would probably either flower very late or not at all. So one of my students is making crosses and looking at what is controlling the flowering mechanism to try to get the uniflower trait into our early season germplasm.”
Cattani and his research group are also doing some initial work on other perennial grain species, such as perennial flax. “There are two native perennial flaxes in Manitoba: Linum lewisii, a blue-flowered flax; and Linum rigidum, a yellow-flowered flax,” he says. “We have collected materials and put them out in the field for the first time this year. They will flower and set seed next year. Then we can start looking at the quality of the oils, whether they could be used for human consumption or are more of an industrial type of oil, or whether they are even stable at all. We don’t know yet.”
Some breeders are developing perennial wheats by crossing intermediate wheatgrass with wheat, usually using winter wheat. However, Cattani notes, “We have tested some perennial wheats here, and none have survived after the first year of production.”
He thinks part of the problem may be the type of winter wheat used in the crosses. “Intermediate wheatgrass has 28 chromosomes, so breeders have been using tetraploid winter wheats, which have 28 chromosomes. From talking to our winter wheat breeders, the winter wheats that survive best in Manitoba have 42 chromosomes. However, crossing intermediate wheatgrass with those wheats would be more difficult.”
Of the grains in his program, Cattani thinks intermediate wheatgrass will likely be commercialized first. “In Manitoba we have a large forage seed production industry, and a number of seed growers have grown intermediate wheatgrass as a certified seed crop. So we know it grows here as a seed crop.”
However, he cautions, “I think we’re probably still 15 to 20 years away from providing producers with an intermediate wheatgrass that has good grain yields consistently over about a five-year period, as opposed to one year of seed yield and four years of hay.
“Often new crops and new concepts are introduced without being properly vetted,” he adds. “Producers might grow it once, but if it’s the crop’s weaknesses that cause it to fail, they will not grow it again. So we want to make sure that when it is released, our intermediate wheatgrass will perform the way we say it does and meets producers’ expectations.”
Successful commercialization also requires a market demand for the product. Food scientists at the University of Minnesota are exploring possible uses of Kernza. “Our current materials have very low gluten. So the flour could be used in things like flatbreads – it makes great pancakes – but to make rising bread products, you’d have to blend it with wheat,” says Cattani. “The food scientists are also looking at how much of the flour you can add without altering the flavour of what is already known to the consumer. I like the flavour of intermediate wheatgrass, but it has a different taste than wheat.”
Cattani sees a wide range of possible benefits from perennial grain production for agriculture on the Prairies.
“You would save time and energy with perennials by not having to prepare the soil and seed annually. And usually, once a perennial crop has established, it is relatively competitive with weeds, unless there is some sort of disturbance,” he says. “With perennials like intermediate wheatgrass, you can use mowing to control weeds rather than applying herbicides.” As well, diversifying a crop rotation by adding a perennial would help reduce weed, insect and disease pressures in the rotation.
Perennial crops are also good at maintaining and improving soil quality. “They tend to return more organic matter to the soil. And they have roots and rhizomes holding the soil together so there is less potential for soil erosion. Plus having the plant material on the soil surface tends to slow down the movement of water across the surface, which reduces the erosion risk.”
Perennials have a longer growing season and they tend to have larger root systems than annuals. So they can usually make use of water and fertility resources over a longer period and a larger area, and may not need as many applied nutrients. “If they are growing in the fall, then their roots are exploring the soil and taking up the nutrients, and the plants will store those nutrients,” says Cattani. “Or if their roots die in the fall, then some of the nutrients are readily available back to the plant in the next spring.
“Another potential benefit of some of these perennial grains is that you could establish them on perhaps Class 3 lands – lands where there are some negatives to annual cropping,” he adds. “So you could produce a perennial food crop on those areas as opposed to only producing a forage crop.”
From an annual yield perspective, perennial grains are at a disadvantage compared to their annual counterparts, because annuals can put a lot more of their resources into seed production. However, this disadvantage can be turned into a positive in a mixed farming production system.
“In the intermediate wheatgrass materials, the best harvest index we have seen so far is in the low 20s. So basically 20 per cent of the plant’s above-ground biomass, or its energy, ends up in the seed,” notes Cattani. “In comparison, crops like wheat have a harvest index up around 40 or 50 per cent. But that also means there is a lot more nutrition left in the aftermath of intermediate wheatgrass. So you could harvest the intermediate wheatgrass’s grain and use it for food or feed it to animals. Then you could graze the aftermath on the field or bale it for use as a supplemental feed. It’s not quality hay, but it has adequate nutrition for a beef animal at certain times of year.”
Cattani doesn’t foresee getting to the point where intermediate wheatgrass would have a similar harvest index to an annual wheat. A perennial plant needs to allocate some of its reserves to structures that allow it to be perennial.
He does think perennial grain crops could eventually be part of perennial polycultures, where two or more crops are grown together in a field. For instance, a polyculture might allow a grower to make good use of different niches within a field or of differing growing conditions from year to year. Another option might be to add a crop that can outcompete troublesome weeds.
Or a grower might add a second perennial food crop, such as Indian breadroot or prairie turnip, which is a nitrogen-fixing legume native to the Prairies. “Indian breadroot has an edible root, which can be dried for storage, used as a vegetable in stew, and so on. Its root thickens over a number of years, and at a certain stage you could harvest it,” explains Cattani. “For instance, if you planted it with a perennial grain, then at the end of six or seven years, you could go into the field and selectively harvest these legume roots as a perennial vegetable. We also have wild perennial onions on the Prairies, which are related to domestic onions. They don’t grow as big, but potentially they could have herb uses.
“Of course, we have to develop the perennial crops first. But we need to start thinking about polyculture and looking into it.”
Various groups around the world are interested in growing perennial food crops as a way to reduce environmental impacts while sustainably feeding the world’s growing population.
For example, some researchers have been examining the ecosystem benefits of these perennials, such as reducing greenhouse gas emissions. Others have been assessing how perennial grains might help in adapting to changing climates and in improving food security. In August 2013, the Food and Agriculture Organization (FAO) of the United Nations held an international meeting called Perennial Crops for Food Security. Participants from around the world examined the best available information on perennial food crops and cropping systems, and discussed their potential for food security, climate change resiliency, ecosystem management and economic opportunities.
“There are researchers looking at perennial wheats, rice, oilseeds, corn and other crops in a number of initiatives, all in their infancy,” says Cattani. “But hopefully we can get more buzz around these concepts to put resources towards at least a good exploration of perennial food crops.” He notes that funding for perennial grain breeding worldwide is only a very small fraction of funding for annual crop breeding.
How does he see the future of perennial grains on the Prairies? “Do I think every farmer will adopt them? No. But I think there is a large enough potential that some growers will, especially in areas with issues like organic matter loss and excessive soil erosion. By including a perennial grain, perennial oilseed or perennial polyculture in their rotation, they will help maintain and possibly improve the health of their soil.”