DES MOINES, Iowa, Oct. 1, 2010 - The Accelerated Yield Technology (AYTTM) system has advanced the seed research and genetic development process, increasing the number of lines tested by nearly tenfold and bringing the best products to market faster, says an expert from Pioneer Hi-Bred, a DuPont business.
The AYT system is a proprietary suite of tools, including molecular breeding techniques, which allows researchers to rapidly scan and identify genes responsible for increasing yields, then incorporate the most favorable genes into elite varieties and hybrids.
"Using molecular markers, we can genetically profile experimental lines and determine a number of genes associated with yield or with resistance to specific pests and diseases," says John Soper, vice president, Pioneer Crop Genetics Research and Development. "Selecting experimental plant lines with specific favorable genes helps Pioneer bring these desired traits more efficiently to growers, resulting in increased rates of genetic improvement, reduced yield variability and improved performance.
"Twenty years ago, the only option for evaluating experimental trait lines would be to grow them and observe the results with our eyes and combines," Soper says. "We'd plant experimental varieties and hybrids in fields with disease or pest pressures. Tolerance to environmental stress was evaluated the same way. To assess brittle snap tolerance in corn, we'd push against the plants to determine how much pressure it took to break the stalks."
Former breeding techniques relied a lot on visual inspection, which limited screening possibilities. However, the AYT system is an improved approach to hybrid and variety development, ensuring Pioneer customers receive the best possible products in the most efficient time frame. Soper says the AYT system allows breeders to begin the process of "unraveling" the genetics responsible for highly complex traits.
"We can use resources more effectively," Soper says. "Unlike field screening of the past, which was always subject to variation - potentially due to the distribution of the pest across a field - molecular marker techniques for simple trait identification are nearly 100 percent accurate with the AYT system because the underlying genetics don't rely on the environment in which we're testing the plant."
The efficiency of molecular markers increases the number of experimental lines a breeder can screen.
"Ten years ago, as a breeder, I might have had the resources to evaluate 1,000 experimental lines for five different diseases, pests or environmental stresses," Soper says. "That approach required me to set up five different, unique screening field nurseries or laboratory screening systems. Many of those, especially field screens, faced tremendous challenges, including non-uniform distribution of diseases, pests or stress in screening fields or the absence of the disease pest or stress altogether due to ever-changing environmental conditions.
"Today, we can evaluate tenfold the number of experimental lines in a shorter time frame, with higher accuracy using molecular marker techniques," he says. "Today's breeder could generate 10,000 experimental lines and use the AYT molecular marker system to screen for resistance or tolerance to the same five diseases and pests using a leaf or seed tissue sample from a single plant. The molecular marker analysis could be used to select the best 1,000 progeny out of the 10,000 based on the genetic profile, indicating which plants possess the best resistance profile, and advance these to field testing for yield evaluation and trait confirmation.
"Using this approach, we're stacking the cards in our favor. It's akin to playing poker with someone who has the cards face down versus you with all the cards face up. By knowing in advance the likely disease, pest and stress profiles of the lines being placed in field trials, we have dramatically increased the probability of identifying high-yielding products for growers that will exhibit performance stability across environments."
Although the company began using molecular markers with soybean breeding in the mid-1990s, Pioneer® brand soybeans continue to reap the benefits of molecular marker technology.
"Among Pioneer soybean series introduced in recent years, about 35 percent of the M series utilized the AYT system and nearly all of the Y Series soybean products were developed using this technology," Soper says. "Pioneer customers have experienced success with these products and can have great confidence planting products with these advanced technologies."
In addition to selecting for genetics that contribute to yield in soybeans, Pioneer attributes gains in defensive traits, such as Asian soybean rust resistance, to the molecular marker technology.
"In soybeans, we've used molecular markers to improve resistance to brown stem rot, soybean aphids, Phytophthora and Asian soybean rust, and we're exploring improvements against frogeye leaf spot, stem canker and others such as white mold and sudden death syndrome (SDS)," he says. "We originally started with traits that would benefit all soybean-growing regions. Now we're extending our efforts to improve regionally important traits such as stem canker resistance in the southern U.S. and iron deficiency chlorosis in the northwest soybean growing regions."
The AYT system began with molecular marker technology in soybeans, but now the system includes several technologies that benefit corn and other crops. Corn breeders use a combination of the following techniques or tools under the AYT system umbrella to screen and evaluate corn genetics:
FAST (Functional Analysis System for Traits)- A combination of high-throughput biotech plant production and automated analysis to evaluate hybrids for traits. The system allows researchers to grow experimental corn in less time than typically required.
Laser-assisted seed selection- A process using lasers to slice off sections of a seed, enabling breeders to review the plant's DNA. Yet it saves enough of the seed for researchers to plant later, as needed.
Doubled-haploid technique- A breeding technique that reduces the amount of time it takes to produce a corn inbred, allowing for more rapid hybrid development from the vast Pioneer genetic library.
Molecular markers- DNA analysis that breeders use to identify the locations of traits of interest. These linked markers allow breeders to select traits in the lab prior to field testing.
- Boreas wind machine- A proprietary, giant mobile wind machine that simulates wind pressure and direction to test stalk and root strength in experimental hybrids.
"In addition to the success of using the latest research tools, we're developing more specifically adapted hybrids and testing even further with IMPACTTM(Intensively Managed Product Advancement, Characterization and Training) trials," Soper says. "These plots provide local testing of multiple products at the last stage before they are advanced for sale to growers. Evaluations take place on growers' farms, and the trials will provide much better quality data collection over the growing season. Because these plots will be managed by professional research teams that will spend ample time at IMPACT trial locations throughout the summer, we'll be able to collect midseason data on agronomic stresses that affect crops, not just yield data."