ASK THE AGRONOMIST BLOG

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.

Last week, we explored how Stine’s agronomy department is looking toward the future by focusing research efforts on germplasm from our Elite Yield Trials that has not yet been commercialized. This week, director of agronomy Tom Larson provides insight on how the agronomy team will leverage Stine’s Success Demos and Side-by-Side Plots to showcase what’s currently available in Stine’s product lineup.

“We already know a lot about the products in our current lineup, but it’s always best practice to learn more,” says Larson. “Our Stine Success Demos and Side-by-Side Plots will be set up with two specific goals in mind — 1.) to train our sales team on how these products perform in any given year, and 2.) to provide our grower customers with showcase plots where they can see firsthand how the products stand up to their environment and against competitors. I also like to call these our show-and-tell plots.”

STINE SUCCESS DEMOS

The goal with the Stine Success Demos is to have two plots per region — one corn and one soybean. All soybeans in the soybean plots will be treated. Corn plots will be planted by relative maturity and population percentage. Since these plots are for training and observation only, they will have four rows, 100 to 150 feet long. The agronomy team will be responsible for monitoring the plots throughout the planting, growing and harvest seasons, keeping tabs on emergence, fungicide/herbicide applications, nutrient inputs, disease and insect observation, and general hybrid/variety observations.

“These plots will be planted and managed by Stine and not a competitor party,” says Larson. “The agronomy team will ensure consistency across all checks and balances — we want the data and our observations of these plots to provide the truest look at how our products perform on a regional level.”

SIDE-BY-SIDE PLOTS

Stine’s Side-by-Side plots are just as they sound. We work directly with our growers or prospective customers to plant one of our products next to a competitor’s product to see how they measure up.

“You might see some farmers who have a big planter fill half of the planter with our seed and the other half with a competitor,” says Larson. “Since Stine genetics are typically shorter in stature than most competitors, we ask that each grower plant a 10 acre block minimum to prevent a shading effect. You’ll always have a point where the two products meet in the field but planting more acres per plot allows customers and those interested in viewing the plot a better picture of real performance.”

A shading effect occurs when a product of a taller stature is planted next to a short-stature product. They might be the same maturity and have similar emergence schedules, but the taller plant will undoubtedly shade out the shorter-stature plant. This limits its access to sunlight and uses up much of the nutrients in the ground as taller material needs more to grow.

“We have a good system in place for customers who wish to plant a Stine Side-by-Side Plot that ensures a level playing ground for both our products and that of our competitors,” says Larson. “We look forward to seeing the results in the field this season.”

Work doesn’t stop with the plots

Although the agronomy team’s core focus will be on planning and implementing the Product Development Plots followed by the Stine Success Demos and Side-by-Side Plots, there’s still a lot of other research going on behind the scenes.

“The agronomy team — we’re definitely not slackers,” Larson jokes. “In addition to our plot program, we’re going into the second year of our seed treatment study for corn and employing our emergence flag study again to monitor emergence, including with treated seed. We’ll be busy, but it’s all worth it to have the resources our sales team needs to better place our seed and for grower customers to understand how our products will perform in their operation.”

Interested in learning more about our plot program and what the agronomy team is up to this year? Connect with a Stine agronomist here.