How Drought-Tolerant Corn Hybrids Measure Up
Written by Dan Wiersma and Ev Thomas*
There's a corn revolution happening on the front lines of drought-prone areas. The combination of drought and heat stress reduces average corn grain and forage production in the U.S. by 10 to 20 percent annually. Demand for corn genetics with better drought tolerance is rising due to more frequent weather extremes, a shift of production to more drought-prone acres, and higher financial risks on the farm.
Breeders have been chasing corn’s drought challenge aggressively for the last two decades. Recently, genetic and biotechnology tools have helped researchers identify many of the complex genetic instructions involved in helping corn plants perform better in low-water growing environments. Future corn hybrid superstars will help plants recover from extreme desiccation and allow them to survive the water and heat stress seen under drought conditions.
Drought Tolerance Strategies
Researchers have been working on breeding hybrids that survive long periods with extremely low water input. While plants prefer to go into survival mode, breeders have identified mechanisms that help plants tolerate the lack of water.
One strategy is to reduce the size of the plant’s leaf surface pores (known as stomata). These small pores regulate water movement into and out of plants. One visible sign of this mechanism at work is less leaf rolling during high-stress times.
Another approach is to synchronize pollination and silking to ensure complete ear pollination and kernel set, even under high heat or water stress conditions. Also, breeders are finding plants with more efficient root systems, helping plants maximize water uptake. Finally, continued disease and insect resistance breeding helps reduce stress and encourages kernel development.
As it turns out, tolerance to drought is a very complicated corn breeding challenge involving multiple genes acting at different times of plant development. Tolerance comes from a systems approach addressing water regulation in the plant, timing of stress tolerance, pollination success, root growth, and pest tolerance.
Three seed companies have introduced genetics to enhance yield under drought and heat-stress growing conditions. DuPont Pioneer introduced Optimum® AQUAmax® hybrids beginning in 2011. Monsanto released Genuity DroughtGard hybrids the following year, followed by Syngenta’s Agrisure Artesian hybrids. Among these hybrid releases, the only company using transgenes (a genetically-engineered trait) is Monsanto. Pioneer and Syngenta have used conventional breeding techniques to achieve high drought tolerance.
Genetic Choices Growing
To gauge progress at improving hybrids for drought tolerance, Pioneer agronomists compared historical and modern hybrids for performance in a water-limited environment in Woodland, Calif. Hybrids planted at 36,000 plants per acre received just 12 inches of irrigation during the season.
The figure shows how modern corn hybrid genetics have improved corn grain yield from 3 bushels per acre per inch of water in the first half of the last century to 10 bushels per acre per inch of water in the 1990s. Drought-tolerant hybrids made even greater gains in recent years, yielding 5 to 7 percent better than other leading hybrids in water-limited environments.
In addition to enhanced performance in water-stressed environments, the latest round of drought-tolerant hybrids perform equally well in normal growing conditions. This means there is no penalty for putting drought-tolerant hybrids in fields that only see occasional water stress.
Corn Silage Improved, Too
Livestock and forage producers growing corn for silage stand to benefit greatly from the development of drought-tolerance corn hybrids. Just like corn grain yield, whole-plant forage yield improves when using drought-tolerant genetics. Another key benefit to drought-tolerant hybrids is the enhanced levels of starch compared to hybrids not designed to withstand water and heat stress.
Most forage growers have experienced feeding drought-stressed corn, where animal performance is typically better due to lower lignin content and higher fiber digestibility. Like other forage crops, there is a trade-off between corn fiber digestibility and forage yield. However, most growers feel yield is most important. Finally, corn hybrids that are able to withstand water and heat stress may develop fewer molds and mycotoxins, reducing feeding concerns of the harvested silage.
Growing drought-tolerant corn hybrids for silage or grain is a key tool for managing risk in your operation. These corn hybrids, however, are not magic and have limitations.
Corn will always need water. But when used in a comprehensive system of soil, water, and crop management, growers will realize the enhanced performance of these modern drought survivors.
*Dan Wiersma is the alfalfa business manager with DuPont Pioneer. Ev Thomas is retired from the William H. Miner Agricultural Research Institute and president of Oak Point Agronomics Ltd.
Used by permission from the June 2016 issue of Hoard’s Dairyman. Copyright 2016 by W.D. Hoard & Sons Company, Fort Atkinson, Wisconsin.