Drought-Tolerant Hybrid Technology Ramping Up
Jim Ruen, 02/11/2013
Drought-tolerant hybrids have come a long way since Wayne Fithian started working with ecofallow, dry land crop production at Colorado State University (CSU) in the early 1980s and with Golden Harvest later. With new technologies in native gene selection, not to mention transgenic gene introduction, dry land corn is poised for even greater advances. Ironically, what Fithian and his CSU colleagues were searching for with arid conditions may prove to be equally valuable in a Midwest dealing with climate change.
"Some of the defensive mechanisms that plants employ to address drought stress are similar to mechanisms to prevent damage from heat or cold stress," said Fithian, product lead, Technical Traits, Syngenta. "In many cases, genes have a broad-based stress response. In others, genes have a more narrow response."
Finding the right response through traditional breeding was literally trial and error through the early 2000s, noted Fithian. He compares it to improving the odds from 1 in 20 to 1 in 15. Even when successful, it was difficult to identify a specific improvement at a specific growth stage. Sometimes these were whole plant characteristics. Sometimes a single characteristic, such as an ear height that ensured a combine snout could get under the ear on a drought-stressed stalk, were selected.
"While we always had a hybrid or two to depend on, we also had to use relative maturity to bolster yield potential under drought," recalled Fithian. "As we approached the late 1990s and early 2000s, drought tolerance had improved across the industry such that growers had more options in hybrids and relative maturities. Now, access to drought-modified hybrids is producing another jump in options and yield potential."
MULTIPLE TECHNIQUES COMBAT DROUGHT
Many of the new hybrids are the result of a combination of traditional breeding techniques and gene marker assisted selections. Others are more refined, traditional approaches. One thing that is uniform across the industry is recognition that drought tolerance, while desirable, cannot detract from yield potential under optimal conditions.
Mapping of the corn genotype and the identification of DNA markers opened the door to the gene marker approach. At Syngenta, this led to the introduction of Agrisure Artesian hybrids. DuPont Pioneer used its Accelerated Yield Technology (AYT) to develop and introduce Optimum AQUAmax hybrids. Using the gene marker approach, specific areas in the genome or specific genes are identified that correlate to drought/stress tolerance.
"We selected for native traits related to drought tolerance as we do for other hybrid traits," said Jerry Harrington, DuPont Pioneer. "Mechanisms identified included stomata control, maintenance of photosynthesis and preservation of leaf area. Some of the traits are still being investigated; however overall, Optimum AQUAmax hybrids tend to stay green, have more root mass and are more closely synchronized in pollination and silking."
In Syngenta's case, that identification process led to identification of 13 different genes that were then validated by crossing them into hybrid lines and comparing their effect against identical material without the genes. Those showing a significant effect under drought conditions were then brought forward in elite hybrids. Fithian noted that combinations of genes assured multiple modes of action to address drought stress throughout the season, as different response mechanisms deal better with stress pre-pollination versus pollination to mid-grain fill and mid-grain fill to maturity.
Addressing drought response in those multiple stages is one reason Mycogen has continued to rely on traditional breeding for drought tolerance, selecting high yielding hybrids that respond.
"The key is to find hybrid lines that perform well in well-watered situations as well as in drought," suggested Lyndall Dallas, product development agronomist, Mycogen Seeds. "It is difficult to expect a single gene to improve tolerance at all three stages, and adding multiple genes adds complexity. We focus on the flowering stage, where stress is most devastating. Tolerant hybrids at that stage tend to develop more consistent ears with more kernels and less kernel abortion."
PLANNING FOR DROUGHT?
Evaluating drought tolerance by appearance at any stage, or eventual impact at one stage versus another, can be difficult, noted Dallas. "While some see leaf rolling as a bad sign, others say it is simply a protective feature. The jury is still out," he said. "If a hybrid handles flowering stress better, it can mask the effect of stress earlier in the season because flowering stress is so important."
He pointed to areas in Illinois that received only one rain in July, but made 190 to 200 bushel yields. He argued that reducing the impact of drought gets down to yield potential. A successful hybrid under drought conditions has to produce optimum yields under optimum conditions as well, he added.
"I don't think we are yet at a point where we can plan for drought," he said. "We need to plan for a good year and select hybrids based on that with the comfort of knowing modern hybrids can withstand drought better than in the past."
Like other seed companies, Monsanto has promoted native trait selected hybrids with drought tolerance. Their introduction of Genuity DroughtGard this season launches a new era as the first to include a transgenic gene for drought resistance. Mark Lawson, yield and stress lead, Monsanto, noted that a limited volume was available this first year. The hybrids that carried it had already been highly rated for drought tolerance. However, the new trait took that tolerance a step further, according to Lawson.
"Under drought stress before pollination, the DeKalb DroughtGard hybrids slow down the rate at which they pull water out of the soil, banking moisture for later," he explained. "This extra water can be used for pollination and seed set to give a greater yield opportunity. However, you still need rain to turn it into true yield."
Monsanto has launched the new trait in the western Great Plains from South Dakota to Texas. Initially, DuPont Pioneer's AQUAmax hybrids are focused mainly on the western Corn Belt, though they will be developed in some lines throughout the market. In 2012, Syngenta offered Agrisure Artesian in nine hybrids across the entire Corn Belt. A substantial percent of available volume was in genetics that best fit the central and eastern Corn Belt.
"Demand was very strong, and those hybrids went fairly fast," said Duane Martin, product lead, Commercial Traits, Syngenta. "Due to the 2012 drought and the exceptional performance of the Agrisure Artesian hybrids this past year, central and eastern growers were equally enthused as those in the western Corn Belt."
EXPANDING CORN'S REACH
Joel Ransom knew his North Dakota growers were not likely to be the earliest beneficiaries of the newest technology in the early maturing hybrids adapted to much of the state. The NDSU extension agronomist recognized that even when growers in northern and western North Dakota are pushing the envelope for water stress, they may not be first on anyone's list. That said, in a state where corn was an anomaly in most counties only a few decades ago, North Dakota enjoyed two national winners in the 2012 National Corn Growers Yield Contest. Jamie Gorder, Wahpeton, N.D., took second in the non-irrigated division. Mike Pikarski, Mooreton, N.D., placed third in no-till/strip-till non-irrigated division at 294.8 bushels. Both were Pioneer hybrids. Although yields are considerably less in most areas, corn can now be found in every county.
"We are getting expansion into really marginal areas," Ransom said. "No-till is widely practiced in the western part of the state today. That really opened a lot of doors to corn where they were pretty well closed in the past."
Ransom noted that corn production really took off about 10 years ago. Although he recognized corn’s increased stress tolerance, he gave more credit to high producing hybrids. "It isn't that drought tolerance is reducing the amount of loss, but rather that with more productive hybrids, we have more left even after the stress," he said.
Ransom gave even more credit to the current price of corn, especially in relation to wheat. "There is potential for a bucket of money, so people want to give corn a try," he said. "If it was half the price of wheat, they wouldn't be that interested."