How to Improve Yield with Genetics
This is the first article in a four-part yield series for the Canola Digest 2021-22 season.
We learned in 2021 (again) that the growing environment plays a huge role in the yield potential of any crop. For canola in Western Canada, excessive heat combined with abnormal dryness is a bad combination for yield, especially when they occur at flowering. Canola has the capacity to rebound from a lot of stress – as long as the plants survive and that stress occurs before flowering.
This article will look at genotype by environment by management (G x E x M) to see how we can take canola productivity to a new level of sophistication and optimization.
Genotype: Select the right cultivar
Early-maturing canola hybrids could have a great fit in Western Canada to avoid heat in summer or frost in the fall. “They also work as a secondary option grown in combination with full-season products as part of a farm production risk management strategy.”
A genotype is the collection or library of genetic traits of a cultivar. Yield potential is based on a complex combination and interaction of traits, including those for pod size, seed size, pod number, root size, nutrient use efficiency, water use efficiency, plant size to seed mass ratio, as well as posted traits like disease resistance, lodging resistance and days to maturity.
The grower’s goal is to find the best canola cultivar for their environment and farming system. The “best” cultivar is often in the eye of the beholder. It could be the one that provides consistent yield year to year under different environmental conditions, the highest yield this year in the nearest trials or the highest yield from among a short list of cultivars that provide the clubroot resistance, pod-shatter tolerance, herbicide system and days to maturity the farmer wants.
Days to maturity (DTM) generated some interesting discussion in canola circles in 2021. This trait relates to flowering date and harvest date, and shorter-season hybrids could help canola dodge major establishment issues and achieve a timely harvest. Dave Kelner, North American canola
portfolio manager with Bayer, says canola growers in North Dakota tend to choose early-maturing cultivars even though the North Dakota growing season is longer than ours north of border. “This isn’t about end of season maturity, but rather the need for earlier flowering to avoid the onset of July heat. These products flower up to a week earlier and mature three to four days sooner than full maturity products,” Kelner says. “Combined with shatter tolerance, early maturity and early seeding, this is a very successful combination for these typically hot, drier environments.”
Kelner says early-maturing canola hybrids could have a great fit in Western Canada to avoid heat in summer or frost in the fall. “They also work as a secondary option grown in combination with full-season products as part of a farm production risk management strategy,” he says.
Days to maturity can be a quirky trait. A “100-day” hybrid might actually mature in 90 days in Manitoba and 110 days in the Peace. Russell Trischuk, BASF’s regional technical services manager for InVigor Canola, explains: “Western Canada is a very large geography and the environmental conditions (e.g. photo period, growing degree days, moisture and soil type, to list a few) that occur across these vast expanses differ significantly, which ultimately has an impact on how long it takes for a certain hybrid to mature across different geographies.”
For this reason, Trischuk says a farmer must recognize that the DTM rating listed for a hybrid is generalized based off data collected across Western Canada. “From a practicality perspective, growers should base their hybrid selection on it being a short-, mid- or long-season hybrid and ultimately recognize that if they are in a long-season zone, maturity may occur a few days sooner whereas in a short-season zone, maturity may take a few extra days,” Trischuk says.
Public breeders in Canada do a lot of behind-the-scenes work to enhance the yield potential of canola. Habibur Rahman at the University of Alberta is one such breeder. Rahman’s canola genetics lab has already turned out clubroot resistance traits that have made it into commercial channels. “Nutrien was the first company to receive the clubroot resistance gene of rutabaga from the University of Alberta,” Rahman says. “This confers resistance to multiple pathotypes, and the company used it extensively in their breeding program.”
Rutabaga is a Brassica napus plant, the same as canola. Rahman is also looking through the genotypes of other canola relatives, including Brassica rapa and B. oleracea lines, looking for traits to improve yield.
Yield potential is based on several genes. “Breeders constantly reshuffle the genes and look for the better gene-combinations,” Rahman says. He says we may soon reach the point where improvements using the current germplasm may become exhausted. “We have to get favourable genes from other sources to broaden the genetic base of canola,” he says.
Rahman sees the B. oleracea genes for earliness as one possible path to higher yields. “If we can get canola flowering earlier,” he says, “this may give the plant a longer duration for grain filling.”
Part of a grower’s seed decision is to select traits that preserve yield potential. Disease resistance traits have been essential ever since blackleg resistance was discovered. These days, growers can now choose hybrids with blackleg resistance that suits the particular blackleg races in their fields. In the near term, yield advantages from disease management will come from clubroot resistance. (See more in the article: Use clubroot-resistant canola early to keep spores low.) The Canola Council of Canada surveyed 1,000 canola growers last winter, and results showed that use of clubroot-resistant hybrids is associated with higher yield in the Black and Grey soil zones.
Habibur Rahman is a canola breeder at the University of Alberta. He’s looking at canola relatives for various yield-enhancing genes, including those for flowering timing. “If we can get canola flowering earlier,” he says, “this may give the plant a longer duration for grain filling.”
Pod shatter tolerance is another trait that can improve yield. Several research projects have shown that yield goes up if canola seeds are given more time to fill before cutting. For any canola hybrid, yield is generally higher if growers swath at 60 per cent seed colour change instead of 30 per cent. For canola with pod shatter tolerance, growers can wait even longer and possibly capture more yield. (See more in the article: Not all shatter pod resistance is the same.)
The next steps in canola yield improvement could come through a focus on complex abiotic stress tolerance traits. These include increased tolerance to cold soils in the spring, increased moisture foraging and moisture retention capabilities, and increased tolerance to summer heat. Again, a lot of this work will start with public breeders. We’ll have more on that in the next section.
Environment: Weather-proof yield
Are you in an area where the environment, especially moisture and humidity, tend to increase disease pressure? Are you in a long-season growing zone? Are you in a region where hot summer days and nights put yield at risk? Seed choices can provide some genetic advantages for these scenarios.
Canola is a cool-season crop that tends to yield best with summer temperatures below 28°C and cool summer nights in combination with timely rains. Canola doesn’t like heat, but some cultivars handle heat better than others. While this trait isn’t publicly tracked and reported, growers could use location results from Canola Performance Trials (canolaperformancetrials.ca) to see how hybrids performed with weather in their regions.
Sonia Wilson, a graduate student with Robert Duncan and Claudio Stasolla at the University of Manitoba, is looking at canola tolerance to excess moisture. “I’m looking for traits that would help a canola plant survive in submerged soils,” Wilson says. “We are observing that some genotypes can survive and recover under submergence conditions better than others.”
Wilson’s experiments include a submergence treatment for seven days. “The main consequence of excess moisture stress is reduced oxygen availability. Oxygen is required to generate energy,” she says. “Some genotypes may perform better than others due to their ability to undergo metabolic changes and alterations in energy-producing processes that allow cells to cope with such low oxygen conditions. These are the genotypes that I am looking to identify.” Duncan and Stasolla are also focusing on drought and heat tolerance.
Baoluo Ma, research scientist with Agriculture and Agri-Food Canada (AAFC) in Ottawa, is using canola genotypes from Robert Duncan’s lab to compare their above- and below-ground response to heat stress. The goal is to understand how increasing temperatures will impact canola growth in terms of root traits, seed yield and lodging resistance. In a 2020 published report, Ma et al showed differences in stem lodging under high temperatures. They also identified a technique to evaluate genotypic differences as they related to heat stress tolerance.
Pre-commercial canola genetics research from Canadian public institutions is an important step in brining improved traits to commercial hybrids. Brad Orr, Corteva marketing leader for Canada, says, “public-private partnerships in plant breeding have the potential to create significant value for farmers and consumers.” Public breeders can do a lot of exploratory work in the gene pool that private breeders may not have the time or budget to do.
“Fundamentally, the partnership is about reducing risk for plant breeding developers that are working towards commercializing a new product concept,” Orr says. “The benefits have the potential to be maximized when collaboration begins early and all partners work towards ensuring that the appropriate regulatory framework and policies are in place.”
Sonia Wilson, a graduate student with Robert Duncan and Claudio Stasolla at the University of Manitoba, is looking at canola tolerance to excess
moisture. “We are observing that some genotypes can survive and recover under submergence conditions better than others,” Wilson says.
Management: Make balanced decisions
The final step in G x E x M is management. Management decisions to improve yield require a weighing of pros and cons with a heavy dose of economics. A big management decision for yield revolves around fertilizer, especially rates, but future genetics work on nutrient use efficiency could be an important part of the G x E x M relationship.
Other management decisions that give a boost to genetics include seeding rate and harvest timing. Canola’s genetic potential for yield is maximized with a stand of five to eight plants per square foot. This is based on detailed analysis by Murray Hartman, retired oilseed specialist with Alberta Agriculture and Forestry, and Steve Shirtliffe, researcher and prof at the University of Saskatchewan.
Canola hybrids yield more if left longer before cutting. With lower seeding rates than in the past, more yield comes from side branches. By cutting at 60 per cent seed colour change, or later, on the main stem, growers give seeds in side branches more time to fill. With traits for pod shatter tolerance, cutting could wait a little longer. This isn’t delayed maturity. Rather, the hybrid is chosen for appropriate maturity for the ecozone, then let stand longer for increased yield and oil content. One thing to note is that hybrids have different levels of pod shatter tolerance, even if advertised as having this trait, so consider the pod shatter limitations of each hybrid.
Fertilizer rates will increase yield, and we’ll dig into that in more detail in the next issue of Canola Digest. For this article on genotype, the management factor to keep in mind is that increased nitrogen can delay maturity, which could take away some of the timing benefit of a short-season hybrid.
A final point on management as it relates to genotype centres on disease resistance. Preserving these valuable traits requires some management, especially with rotations. A two-year break between growing canola on the same field goes a long way to protecting the viability of clubroot resistance in particular.
Canola yield potential will continue to increase as public and private breeders keep shuffling genes, bringing in new genes from close relatives, and using new tools to identify more complex traits like cold tolerance and nitrogen use efficiency. Hand in hand with that, growers have many management steps that can help them get the most out of the yield potential currently available. Benefits of these practices can be hard to see in a year where “E” so strongly influenced the G x E x M relationship. Here’s hoping that 2022 allows canola growers to see how genotype and environment and management decisions interact to actually improve canola yield.