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Research, genetics and data are what set Stine’s corn breeding program apart from industry competitors. Stine^® hybrid seed corn is developed on a foundation of science, and the material we place in growers’ fields is time tested for proven performance. Over the last few weeks, we’ve explored how the birth of a hybrid begins at the Stine Seed Farm through inbred development and our self-pollinating process and how it advances through our nursery in South America to continue the selfing process. To cap off our series, we dive into our unique Pre-Elite and Elite Yield Trials and how our hybrid seed corn completes the final steps to prepare for launch in the marketplace. 

For 21 years, Stine’s head of corn research Jason Behn has worked within the ebbs and flows of our corn breeding program. He’s spent many years researching, testing and bringing new corn hybrids to market. This year, he and his team are testing nearly 50,000 new hybrids through our Pre-Elite Trials program in 42 yield trial locations throughout the Corn Belt, ranging from North Dakota to Missouri and Michigan.

“Evaluating corn inbreds is an extremely important component of our corn breeding program,” says Behn. “It’s these inbreds that we cross to make our ‘test hybrids’ that advance through our Pre-Elite Trials. These are the hybrids that, through our research in the early stages of our program, have displayed a strong genetic background from their inbred parents. We won’t advance anything that doesn’t perform and that the data doesn’t back.”

What are Stine’s Pre-Elite Trials?

Stine’s Pre-Elite Trials are Stop 1 in a hybrid’s journey to commercialization. These hybrids have never been tested against other hybrids before. It’s here that they are “checked” against our current products in the system.

“Uniformity is key to our Pre-Elite Trials,” says Behn. “We make sure every variable is aligned, including fertilizer and herbicide applications, the soil types the hybrids are placed in, planting space and population. We even have a planter that is designed with compaction in mind so that every hybrid has the same tire tracks going by it. All hybrids have an equal playing field throughout the season in our Pre-Elite Trials.”

Before hybrids are placed in Pre-Elite Trials, they are grouped by maturity. The genetic background of the hybrid’s parents helps us determine the maturity of our test hybrids. It’s critical that each hybrid is planted in its correct maturity zone.

Once the hybrids have undergone a growing and harvest season in one of our 42 Pre-Elite Yield Trial locations, only the top-performing testers advance.

“Only 5% to 10% of test hybrids advance to the next phase in our program — Elite Yield Trials,” says Behn. “The hybrids that don’t make it through are disposed of. If they don’t show strong potential in our Pre-Elites and up against what’s in our current lineup in the market, there’s no value in moving them forward. Our vetting system is very thorough; we know that we’re advancing the right products each year.”

Once a hybrid “graduates” from the Pre-Elite Trials, their inbred parents undergo more selfing reps in our South American winter nurseries in Argentina and Guyana so that we can produce more material from both parents for additional hybrid crosses.

 “A finished inbred is generally F7 or higher, so we continue to self the inbreds before Elite Yield Trials to get that material to the F6 and F7 level,” says Behn. “With each selfing generation, we’re lowering the heterosis, or simply continuing to purify the inbred.”

What comes next in our corn breeding program?

Stine’s Elite Yield Trials are the final stop on a hybrid’s path to commercialization. Hybrids typically spend up to two to three years in our Elite Yield Trials before advancing to market to ensure they have consistently met all performance checks throughout the program.

“In our Elite Yield Trials, we have more reps than our Pre-Elite Trials, meaning we plant more seed and conduct more research,” says Behn. “This allows us to review more data points, which ultimately ensures we’re looking at how that hybrid performs against several different environmental and agronomic variables. Only the best of the best advance, so it takes time and diligence to sort out the true and consistent top performers.”

In our Elite Yield Trials, new hybrids are evaluated not only against our current material in the lineup but also competitor hybrids. Like our Pre-Elite Trials, we ensure consistency in uniformity. We test all hybrids under multiple populations, row configurations and environments, but we do so in a way that ensures each hybrid, even our competitors’, is getting equal treatment.  

“What’s a bit unique about our Elite Yield Trials is that we test in varying row configurations, including three 15-inch rows and then a 30-inch gap between the test hybrids,” says Behn. “That allows us to test the hybrids in multiple populations. The middle row is getting tested at a higher rate than the two outside rows. This gives us more data on how it will perform in different environments, row spacing and populations — something that makes Stine’s breeding program unique and helpful in providing a real-world look at how these hybrids will perform when they hit the field.” 

Once a hybrid has proven itself, we take time to build up the seed stock so that it’s available to our grower customers. This occurs at our winter corn nurseries in South America and throughout our plot system in the U.S. From there, we begin the trait conversion process, where our top-performing material is combined with industry-leading traits. We also reserve conventional seed for growers who want high yield but without the addition of a trait.

“Even our conventional seed is the best out there,” says Behn. “We divide the good from the OK or even bad in our Pre-Elite and Elite Yield Trials so that, no matter the hybrid, growers are truly getting the highest-performing option in the bag. We don’t breed one-hit wonders in our program; our process and testing won’t allow it.”

To learn more about Stine’s industry-leading corn breeding programs and our selection of high-yielding corn products for the 2024 season, contact your local Stine sales rep today.

Stine^® hybrid seed corn goes through an extensive process before it’s released for commercialization. In last week’s article, we explored what makes our corn breeding program more efficient than others in the industry, and the beginning stages of corn development at our nursery on the Stine Seed Farm. This week, we discuss new inbred development, which is another important step in our corn breeding program.

How are new inbreds developed?

“New inbreds are developed by making crosses between inbreds that have successfully completed the final stage of yield trials,” says Warren Stine, assistant director of corn research. “These crosses are made either in isolation blocks or in the nursery. Seed from these crosses is then shipped to our winter nursery in Guyana, where it is planted in late November and then self-pollinated, or ‘selfed.’”

Once the seed reaches Guyana, our team onsite will harvest the seed in February (Generation 1) and then plant it and self it again to harvest in May (Generation 2). This seed will be planted, selfed and harvested again in August (Generation 3) and then again in November (Generation 4). Each individual cross from the prior year, which originated on the Stine Seed Farm nursery in Adel, is now assigned a population number, and each ear harvested from that population is assigned a line number.

“Each generation of selfing drives a process of genetic recombination during which new characteristics start to segregate out,” says Stine. “After three generations of selfing, individual plants have an ear that is unique and stable enough to test yield.”

Each line (ear) will have some seed placed in an isolation block where it will be used as a female for crossing to make a test hybrid. The seed from the line (ear) not placed in the isolation block is shipped back to Adel, where it is selfed in the Adel nursery. The hybrid seed created in the Guyana isolation block are placed in Stine’s Pre-Elite testing program.

“Crosses made this year in Iowa will go to Guyana and spend all of 2024 there,” says Stine. “In 2025, the progeny and hybrid test seed from those crosses will return to Iowa. The hybrids go into the yield trial, and the inbreds go into the nursery for selfing.”

What are corn isolation blocks?

Corn isolation blocks are important to developing new corn inbreds. Essentially, they are fields that are isolated from outside sources of pollen. This ensures purity in the product, where no external source can pollinate the female inbreds. The fields are isolated either by date or space.

“We use isolation blocks to increase seed stock and create hybrid crosses and new population crosses,” says Stine. “These fields always have one male inbred serving as a pollen source. All female inbreds are required to be detasseled. Several thousand unique female inbreds can be used in a single isolation block.”

The detasseling process in isolation blocks is a critical step and requires daily walking for tassels until all female inbreds are completely detasseled. As these females are of varying maturities, the detasseling process can take several weeks. This year, on the Stine Seed Farm, we have roughly 207 acres split between 50 isolation blocks. Planting dates were April 28 to June 12. The blocks were planted in a six and two pattern, and we used 121,013 row tags, or about 19 miles worth of tags to mark inbreds.

Now that we’ve explored how inbreds are developed and used in our corn breeding program, next week we’ll focus on how hybrids and conventional seed corn advance through Stine corn yield trials and, eventually, to commercialization. Stay tuned for Part 3 next Thursday.

As one of the largest independent corn seed companies in the United States, Stine^® has a unique advantage in the industry. We are family owned, and that independence ensures we are not beholden to corporate boards or red tape that may slow down processes. Harry Stine — our founder — started the company with a farmer-first mentality, which carries over to our breeding programs.

“As a farmer himself, my dad would never put a product on a grower’s farm that he wouldn’t put on his own operation,” says Warren Stine, assistant director of corn research. “Because of our independence and flexibility, we’re able to operate one of the industry’s largest and most prolific corn breeding programs while staying true to the principles of farming.”

In his position, Warren works in our corn nursery, where Stine’s corn breeding program begins.  

How does corn breeding work?

At the Stine nursery — located on the original Stine Seed Farm in Adel, Iowa — we develop and maintain corn inbreds for Stine’s commercial product lineup and our hybrid yield trial testing system. Corn inbreds are essential to the production of making hybrids; they are considered the parents. Each hybrid requires two inbred parents: one male and one female.

“To create a stable inbred for commercial use requires about eight generations of self-pollinating. The Stine nursery is primarily for doing self-pollinations,” says Stine. “As corn is a naturally cross-pollinated crop, all self-pollinations must be controlled and done by hand. Soybeans, on the other hand, are naturally self-pollinated, so they do not require any of the extra work that corn requires.”

How do you pollinate corn?

Stine corn is pollinated through a three-step process, which includes:

1. Covering the ear shoots with a shoot bag before the shoots have silks.
2. Setting up tassel bags once both silks and pollen are produced.
3. Shaking the pollen into the tassel bag and then removing the tassel bag and placing it over the ear shoot. Then, we sprinkle the pollen onto the silks.

Our corn nursery is approximately 39 acres this year — the largest we’ve ever had. We planted on four different planting dates, two weeks apart, starting in May and ending in June. This year, we have a total of 77,780 rows of inbred parents represented by approximately 58,000 hybrids in testing. We expect to do 650,000 hand pollinations, which takes roughly two tons of shoot bags, 14 tons of tassel bags and 80 pounds of staples.

“Self-pollinating corn is a tedious process, but it’s a critical step to breeding corn hybrids,” says Stine. “And we’re fortunate to have our corn breeding program down to a science to ensure that only the best inbreds advance to create top-performing hybrids. We’re not afraid to throw out what doesn’t work. It’s truly a numbers game, and the more inbreds we evaluate, the more material we have to produce the best corn hybrids on the market.”

Stay tuned for Part 2 in our corn breeding program series where we dive into our corn isolation blocks, new inbred development and corn yield trials.