HEADS UP
BY JEANINE MOYER • PHOTOS COURTESY OF AMY DELAQUIS
Canadian wheat breeders and researchers agree on three things: lodging is a serious concern for Prairie wheat farmers, stem strength isn’t the only factor that affects lodging and more research is needed to find agronomic and genetic responses.
Sources contacted by GrainsWest could not cite statistics on the prevalence or economic impact of wheat lodging, but Anne Kirk, Manitoba Agriculture cereal crop specialist, said lodging routinely inflicts yield loss. According to Kirk, yield reduction is greatest when wheat is lodged flat at anthesis (flowering) or in the early stages of grain filling. During this window, yield loss from lodging can range from 10 to 40 per cent, and as high as 80 per cent. “The amount of yield loss depends on cultivar susceptibility to lodging, growth stage, severity, wind and rain events,” she said.
As Kirk noted, lodging isn’t the result of one culprit, and a host of variables can affect its prevalence in wheat. These include agronomic practices such as seeding rate, soil moisture level, insect populations, variety selection and weather. Heavy wind with rain can be especially damaging. Lodging can occur throughout crop development but is most often seen during the grain filling stage when a plant’s weight shifts to its upper section.
As lodging is known to diminish crop yield and quality, it naturally results in economic loss. According to Gurcharn Singh Brar, assistant professor and wheat breeder at the University of Alberta, cumulative losses can add up to a substantial economic hit for the wheat sector. “Lodging is one of the most important agronomic traits in wheat because it can have so much influence on a grower’s yield and quality,” said Brar. “But the challenge is that the causes are not black and white. Breeders are trying to improve resistance by selecting lines with acceptable or minimal lodging, but more research is clearly needed to identify stem and root traits that can be used to create new, elite varieties.”
Brar also noted that even with the most resistant lodging varieties, weather can be the determining factor in the standability of a wheat crop. Soil moisture and wind contribute to lodging, he said, but geographical variances in environmental conditions also contribute significantly. Elevation may also be a factor, he said, and cited the variation in lodging incidence between the Edmonton and Lacombe areas, which is approximately 200 metres higher.
“Historically, Lacombe has a higher frequency of lodging, compared to other growing regions,” he said. “This is why it is so important that lodging research variety trials continue to be conducted across Western Canada to account for the variation in environmental growing conditions.”
THE GENETICS OF LODGING
Ginelle Grenier, a University of Manitoba PhD candidate spent five years analyzing the genetic component of lodging resistance in spring wheat. Her research evaluated 181 spring wheat cultivars from both indoor and outdoor field trials conducted in Manitoba from 2020 to 2024.
Grenier aimed to identify sections of the wheat genome and genes that regulate lodging resistance traits in spring wheat to pinpoint the mechanisms behind lodging resistance. She hopes her work will give fellow cereal researchers and breeders such as Brar new genetic tools to mitigate lodging in new wheat cultivars.
“Historically, lodging has been managed by practices focused on lowering plant height,” said Grenier. In many cases, shortness limits yield potential due to the reduction in total photosynthetic plant material. “That’s why this is a prime area of research—identifying alternative traits other than plant height that affect standability and lodging resistance. Our goal is to develop molecular tools to increase lodging resistance that can be used in breeding elite wheat cultivars.”
The process involves the identification of genetic markers that can be used by plant breeders to speed up the selection of wheat lines and more effectively identify lodging resistance traits. “We focused on finding alternative traits that contributed to lodging resistance in the stem, like diameter, breaking strength and stem weight to find additional ways to manage lodging,” she said.
The study assessed plant responses in field and greenhouse trials. To identify zones of the wheat genome associated with stem lodging traits, Grenier used genetic mapping and RNA sequencing, which is the measurement of gene expression through the presence of distinct plant characteristics.
As a tool to control wheat lodging, few studies have sought to identify genetic regions for traits other than plant height. “This research approach of combining RNA sequencing with genetic mapping helps to paint a full picture of lodging response in wheat and makes it easier to identify the genetic regions likely regulating lodging resistance traits,” said Grenier. A better understanding of how plant traits other than height contribute to lodging resistance will benefit research and breeding for western Canadian wheat.
“Evaluating the gene expression through RNA sequencing allows us to better understand the molecular mechanisms in the plant that regulate these physical traits,” said Grenier. The research revealed a connection between the occurrence of lodging and the genes thought to be responsible for resistance and susceptibility. “We can connect the two—physical and genetic expressions—to identify the genes that likely contribute to lodging traits.”
The study revealed some of the tallest wheat varieties had higher lodging resistance and stronger stances than shorter varieties. This finding emphasized the need to look for traits beyond plant height to manage lodging. Traits such as stem strength, internode lengths and stem weight may contribute to resistance, said Grenier.
“This project highlighted just how complex the trait of lodging resistance is and how the occurrence of lodging in spring wheat is influenced by many internal and external factors,” she added. “The more we can learn about lodging, the more we can provide tools to help our growers and industry make informed decisions about management practices and future plant breeding to improve lodging resistance.”
PRACTICAL FIELD SOLUTIONS
Amy Delaquis also conducted a PhD study at the University of Manitoba on management practices that contribute to improved yield efficiencies and decreased lodging potential in spring wheat. The in-field research was conducted over 2018 and 2019, with the results published in 2022.
“It’s hard to quantify how much lodging impacts spring wheat production across the Prairies because occurrence is extremely variable between fields, across fields and growing seasons,” said Delaquis. “The intent of this study was to provide Prairie farmers with management options that can be easily implemented on farms to minimize lodging risk while still pushing for high yield and protein levels.”
The goal was to identify major factors that contribute to root and shoot lodging in current production systems and provide practical recommendations. Delaquis evaluated how nitrogen management, plant density, plant growth regulator (PGR) applications and their interactions influenced lodging risk, grain yield and protein content. She also set out to understand how these on-farm agronomic practices influence the development of grain yield and protein.
Throughout her field trial research, Delaquis was surprised root lodging, which occurs when the stem leans away from the crown due to unstable roots, was the most common type of lodging. Stem lodging, the bending or snapping of the plant stem, was much less prevalent. This observation led Delaquis to develop management recommendations that take root lodging pressure into account.
Since the release of Delaquis’s results in 2021, Prairie wheat growers have experienced several seasons with higher lodging rates. This has driven renewed interest in easy-to-implement solutions to reduce lodging while delivering desired protein and yield.
More research is required to improve lodging resistance in wheat. For now, Prairie farmers can rely on the discoveries and improvements being made by scientists and breeders who are committed to the improvement in production and resilience of the region’s wheat.
Mitigation in practice
Delaquis’s project delivered practical recommendations to minimize wheat lodging risk on western Canadian farms.
Split nitrogen applications
Nitrogen applications split between seeding and flag leaf, rather than entirely at seeding, did reduce lodging. This was attributed to increased stalk strength, reduced vegetative growth and, at times, increased anchorage strength. This practice also produced the same yield and protein as similar nitrogen rates applied entirely at seeding.
The practice may reduce early season nitrogen loss and allows a farmer to adjust total nitrogen rates based on in-season growing conditions. The method does require precipitation for nitrogen incorporation, an additional pass in the field and use of specialized equipment and fertilizer.
Reduce plant densities
Reduction of plant density from 35 plants/ft2 to 25 plants/ft2 increased resistance to lodging. Crops with lower plant densities had greater stem diameter, stem strength and elasticity. They also developed a larger structural rooting area and anchorage strength. Lower plant density of 25 plants/ft2 did not affect grain yield and protein.
Reduction of plant density reduces seeding cost but also decreases plant competitiveness against weeds in the early season. This approach can increase the variability of crop stage development.
PGRs work
PGR application to reduce lodging is a common practice across the Prairies. This project confirmed its effectiveness. PGR applications reduced lodging risk and delivered small increases in yield between one and 2.5 bu/ac. Lower canopy height reduced lodging, increased stem strength and, at times, increased structural rooting area.
PGR application offers flexibility to make in-season decisions. A decision to apply a PGR can be made following an assessment of soil moisture level, growth conditions and environmental factors. Yield increase may also cover the cost of the application.
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