Exploring the Potential for Reduced-Stature Corn
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Crop Insights
Written by Robert Gunzenhauser, Pioneer Research Scientist
Key Points
- Reduction of plant height has been an important innovation for increasing yields in wheat and rice by increasing the harvest index and making plants less prone to lodging.
- In corn, more than 25 single gene mutations have been identified that affect plant structure. These mutations generally fall into two effect categories – influence on hormone levels or influence on hormone response.
- The potential for developing reduced-stature corn has been explored for decades, with research by Corteva Agriscience’s legacy companies dating back as far as the 1940s.
- Reducing plant height in corn makes the plants better able to withstand high winds and increases accessibility for in-season applications without the need for high-clearance or aerial equipment.
- Research and development at Corteva Agriscience are presently being performed to bring the best genetics to farmers’ fields and the management guidance for greatest benefit with reduced-stature corn.
Higher Yield Through Shorter Plants
Reduced-stature corn (RSC), also referred to as “dwarf” or “short” corn, is a concept that has received increased attention in recent years. Reduction of plant height has been an important innovation in other crops such as wheat and rice but so far has not been successfully deployed in corn, despite numerous attempts over the past several decades. Today, the need to continue driving higher yield in corn as well as increase resilience against severe weather has brought about a renewed focus on the concept of reduced-stature corn. This Crop Insights provides an overview on how reduced-stature corn is developed, the intended benefits, and some of the agronomic considerations that are being studied by Corteva Agriscience.
Figure 1. A research trial of Corteva Agriscience reduced-stature corn being harvested with a plot combine.
Reducing Plant Height in Corn
Improving the yield and standability of grain crops by reducing plant height has played an important role in global food production and food security over the past 70 years. The breeding of dwarf crops gained traction in the early 1950s with the introduction of semi-dwarf wheat varieties developed by Norman Borlaug after crossing a dwarf Japanese variety, ‘Norin 10’, with various Mexican varieties. The benefit of the resulting semi-dwarf wheat varieties was reduced lodging of the crop, especially under higher nitrogen and irrigation applications. Another benefit was that more energy and nutrients went into grain development, leading to an increased harvest index (ratio between grain mass and total above ground biomass). This generated greater yields and made Mexico self-sufficient in wheat production shortly after development. This in turn lead to the Green Revolution with the semi-dwarf wheat varieties finding their way to India and Pakistan. This same approach of breeding dwarf genes into crops has been used in rice and sorghum as well.
In corn, more than 25 single gene mutations have been identified that affect plant structure. These mutations generally fall into two effect categories – influence on hormone levels or influence on hormone response. For the gene mutations that influence hormone levels, gibberellic acids are the primary focus. They promote stem and internode elongation, along with many other physical traits. Plant varieties with identified genes that are either GA-deficient or GA-insensitive tend to have shorter stature than wild-type cultivars. These genes can be altered by biotechnology processes or bred into improved genetics to generate reduced-stature varieties.
The potential utility of reduced-stature corn has been evaluated by Pioneer in the past. Efforts at developing “dwarf corn” took place in the late 1940s (Figure 2). An article published in the July 1960 Pioneer Kernels newsletter summarized findings of contemporary research on dwarf corn hybrids. The article stated that, based on experiments conducted in the prior year, dwarf hybrids did offer improved lodging resistance, but did not compete in yield with the then-current standard stature hybrids, and that unfavorable growing conditions could make the dwarf hybrids place ears too low for mechanical picking. However, the article was hopeful that certain dwarf traits could be bred into taller varieties to reduce plant height without losing yield or creating ear placement concerns.
Figure 2. Images that appeared in the Pioneer Kernels Newsletter in the late-1940s showcasing early work by Pioneer Hi-Bred with dwarf hybrid corn.
Why The Renewed Interest in Reduced-Stature Corn Now?
One of the factors leading to renewed interest in reduced-stature corn was the August 2020 derecho wind event that hit the Central Corn Belt in the Midwestern U.S., knocking over millions of acres of corn with sustained wind speeds 70 to 120 miles-per-hour (Figure 3). In many cases the corn was flattened so much that it could not be harvested and had to be destroyed through shredding and tillage (Figure 4).
Figure 3. August 10, 2020 derecho: Lowest angle NWS radar reflectivity at one-hour time steps (NWS Chicago).
Figure 4. A corn field flattened by the high winds of the August 2020 derecho near Adel, Iowa. Photo: Lisa Schmitz - National Weather Service (Des Moines Office).
The 2020 derecho was a unique in its scale and severity but was also part of a broader trend of more intense and damaging wind events. The central U.S. has experienced an increase in the frequency and intensity of severe straight line wind events over the past 40 years due to rising temperatures (Prein, 2023). As this trend continues to intensify in coming years, so too will the risk of corn yield loss due to wind-induced lodging. Making corn plants better able to withstand high winds will be an important component of building more stable and resilient agricultural systems.
Even before this massive wind event galvanized renewed interest in reduced-stature corn, scientists at Corteva Agriscience and its legacy companies had been developing and testing reduced-stature corn for over 20 years through various biotech and breeding programs. Over the course of this period, scientists evaluated multiple genes and approaches for incorporating reduced stature into elite corn genetics. Some genes and approaches were not successful; much like previous attempts, they were able to achieve reduced stature in corn but not without compromising yield and/or harvestability. The approach currently being tested appears to offer the best combination of yield potential, resistance to lodging, and harvestability.
Figure 5. Standard stature corn (top) and reduced-stature corn (above) at the V8 growth stage.
Characteristics Of Corteva Agriscience’s Reduced-Stature Corn
Reduced-stature corn that has been developed and is currently being evaluated by researchers at Corteva Agriscience is typically 60 to 76 inches tall (152 to 193 cm) at full height, with an ear height of 24 to 36 inches (61 to 91 cm) under typical growing conditions (Figure 6). Reduction in plant stature is achieved by uniformly reducing the length of internode distances between leaves over the entire height of the plant.
Reduced-stature plants have the same number of leaves as standard-stature corn with similar relative maturity; however, the leaves are typically shorter in length and wider. Leaf area index (the total amount of leaf area per unit area) is very similar between reduced- and standard-stature corn, which is critical for maximizing light capture and yield potential.
Figure 6. Reduced-stature corn next to a current commercial hybrid in the Corteva Agriscience field demonstration plots at Johnston, IA., July 2023.
Stalks are generally 10-25% larger in diameter in reduced-stature corn compared to standard-stature (1-1/8 inches (2.8 cm) for RSC vs ¾ - 1 inches (1.9 to 2.5 cm) for SSC). Reduced-stature corn can also be more prolific (multiple ears per plant) and produce more tillers than standard-stature hybrids in some instances. The reduction in stalk length means that reduced-stature corn has less aboveground biomass than standard-stature corn, which may offer an advantage in areas where residue management is a challenge.
Figure 7. A block of reduced-stature corn surrounded by severely lodged standard-stature corn at the Corteva Agriscience Marion, IA, research station following a severe wind event in August 2021. Photo courtesy of Deborah Montezano.
Benefits Of Reduced-Stature Corn
Reduced-stature corn is less likely to be lodged, or blown over, during high wind events, due to its shorter profile and thicker stalks (Figure 7). Reduced-stature corn has been tested by Corteva Agriscience using its Boreas wind machines for green snap and root lodging and was found to lodge much less than standard-stature corn (Figure 8).
Figure 8. Corteva Agriscience’s Boreas wind machine creates winds that can exceed 100 miles per hour to test for standability in corn hybrids.
Another benefit of reduced-stature corn includes the ability to perform later season applications of pesticides and fertilizer with conventional application equipment, not necessarily high-clearance machinery. Most modern applicator machines can clear the reduced-stature corn to make field applications at or after tassel.
Agronomic Considerations
Reduced-stature corn brings with it a set of questions often raised by farmers, especially in management and cropping operations. Changes in corn canopy architecture and biomass allocation over the years have come about gradually through decades of corn breeding. Reduced-stature corn represents an abrupt change in multiple plant characteristics. Leaves are shorter and wider and the vertical distance between leaves, as well as the depth of the crop canopy overall, is reduced. Changes in the architecture of the corn plant could require changes in how those plants are managed.
Figure 9. Field demonstration of reduced-stature and standard stature corn at mid-vegetative growth stage (top) and near physiological maturity (above) at the Corteva Agriscience research center at Johnston, IA., 2023.
The first question that often arises with regards to reduced-stature corn is whether reduced-stature corn will require a row-spacing narrower than 30 inches in order to achieve sufficient light interception to maximize yield. The vast majority of corn acres in the U.S. and Canada are currently planted in 30-inch rows. To maximize yield, the crop canopy needs to capture 95% or more of photosynthetically active radiation (PAR) during the critical period immediately before and after silking. Several studies have shown that corn planted in 30-inch rows is generally able to do this in the Midwestern U.S. Research is currently ongoing to determine if row spacings narrower than 30 inches would benefit the yield of reduced-stature corn, or if this can be addressed through breeding and selection.
Another area of interest is the optimal seeding density of reduced-stature corn genetics. Again, the question is raised due to the smaller plant footprint and whether this creates an opportunity to place plants closer together for more yield. Initial work at Corteva Agriscience suggests that seeding densities do not need to be greatly different than similar standard-stature genetics. However, more investigation into this area is needed and research is on-going.
Figure 10. Reduced-stature corn at a density of 40,000 plants/acre in the Corteva Agriscience field demonstration plots at Johnston, IA., July 2023. Click here or on the image above for a larger view.
Harvestability of reduced-stature corn is often a question raised by farmers. Because the plant is shorter, so is the placement of the ear. Farmers may recall drought years when corn growth development was stunted and perceived difficulty in harvesting the shortened plants and raise similar questions about reduced-stature hybrids. Selection for hybrids that place ears at least 24 inches (60 centimeters) above the ground is important to allow the harvester head to capture the stalk and pull the ear into the harvester.
Summary
Reduced-stature corn is a new generation of corn genetics that address specific issues around wind lodging and late-season operations. Research and development at Corteva Agriscience are presently being performed to bring the best genetics to farmers’ fields and the management guidance for greatest benefit for reduced-stature corn.
References
- Ferrero-Serrano, A., C. Cantos, and S.M. Assmann. 2019. The role of dwarfing traits in historical and modern agriculture with a focus on rice. Cold Spring Harb. Perspect. Biol. 11:a034645.
- Hedden, P. 2003. The genes of the Green Revolution. Trends in Genetics. 19:5-9.
- Prein, A.F. 2023. Thunderstorm straight line winds intensify with climate change. Nature Climate Change. Nov 2:1-7.
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