For corn farmers, choosing hybrids usually comes down to a familiar question: Which ones will yield the most on my ground?
University of Minnesota corn geneticist Candy Hirsch is looking at a question farther upstream — one that could influence which hybrids farmers have to choose from years from now. The question: Will the genetic diversity needed to keep corn productive in an increasingly unpredictable world still be available when plant breeders need it?
That matters because the next generation of corn hybrids may need to deal with more variable weather, emerging disease pressures, changing cropping systems and increasing demands for better grain quality.
Hirsch, who has led the university’s corn genetics program since 2013, studies traits ranging from corn’s pan genome and root architecture to grain durability and how hybrids perform in different production systems.
Her lab is using DNA sequencing, drones and artificial intelligence to identify better genetic traits and better understand how corn responds when growing conditions turn against it.
More Genes Than You Think
Hirsch’s work with the corn pan genome starts with a simple premise: No single corn hybrid or inbred line contains all the genetic variation available in the crop.
An individual corn plant carries roughly 40,000 genes. The collective corn pan genome, however, contains more than 100,000 genes, Hirsch says.
Think of it as the difference between one book and an entire library.
Some of that genetic variation isn’t represented in today’s commercial corn genetics. Yet it could contain material breeders eventually need — including disease resistance or stress tolerance that may have been left behind as breeding programs focus on yield and other priorities.
“We have to tap into this diversity now to build the varieties we need to meet the climatic conditions of the future,” Hirsch says.
That makes genetic diversity a resource worth preserving, she adds, before breeders know exactly which genes they will need.
A Genetic Insurance Policy At Risk
Some of that diversity is stored in germplasm collections and gene banks, but maintaining it isn’t simple or necessarily easy.
The USDA corn collection in Ames, Iowa, holds about 20,000 distinct samples of corn genetic material, known as accessions Hirsch says roughly half either have too little seed to distribute or haven’t been regenerated in more than 30 years, leaving some of that material with questionable viability.
If a unique gene exists only in an accession that’s essentially lost, breeders can’t use it.
For farmers, that makes genetic conservation more important than ever. A trait can’t be bred into a future hybrid if the genetic source of that trait no longer exists.
Hirsch and her colleagues are using sequencing and other technologies to help determine which accessions need to be maintained.
The goal is to preserve as much useful diversity as possible while making efficient use of limited resources.
What Drones Can Tell Breeders
Hirsch’s lab is also using drone-based high-throughput phenotyping to study how different corn genetics respond to field conditions.
Instead of measuring plant height or other characteristics manually, researchers use drone imagery to build 3D reconstructions and measure individual plants or plots repeatedly throughout the growing season.
That gives researchers a way to watch how plants respond as weather conditions change.
When a stress event occurs, they can compare plants afterward to see which genotypes continue growing, recover or fall behind.
For breeders, that’s important information.
The goal isn’t to just identify hybrids that win under ideal conditions. It’s to understand how different genetics respond when conditions aren’t ideal — information that could help breeders develop corn with more consistent performance across a wider range of environments.
Grain Durability: An Increasingly Important Quality
Another area of Hirsch’s research involves a trait farmers may not think much about until grain starts moving through post-harvest systems: durability.
Her research indicates grain durability has declined over time, potentially creating negative economic consequences after harvest.
Corn can grade well when it first comes out of the field, but kernels still have to make it through dryers, augers, grain legs, transportation and other handling processes before reaching the end user.
If kernels break along the way, grain quality suffers and farmers can lose ROI.
Hirsch’s team is working to identify the properties that contribute to grain durability, so breeders can continue selecting for yield without making kernels more fragile.
Durability isn’t a trait that can be separated neatly from the rest of the production system, she says. Genetics, environment and management all influence durability, including how and when corn is grown and harvested.
Hybrids Built For How You Farm
Hirsch also is examining whether the production system itself should become part of the hybrid-selection equation.
Her team is studying genotype-by-cropping-system interactions — essentially asking whether breeders should develop hybrids with specific production systems in mind rather than assuming the same genetics will perform equally well in any system.
That’s becoming more relevant as farmers adopt cover crops, intercropping and other agronomic and management practices.
For example, researchers are using drone imagery to identify varieties that emerge and grow differently through cover crops, including
hybrids that clear the cover crop faster and those that struggle early on.
Such research could eventually give farmers another factor to consider when selecting hybrids: not just which hybrid yields best, but which genetics fit the type of production system the farmer is using.
Getting To The Root Of Stress Tolerance
Hirsch also is digging into the roles corn roots play in development.
Roots influence water and nutrient uptake and can affect standability, making them an important piece of the plant’s ability to deal with stress.
The challenge is that roots are notoriously difficult to study, she says. Much of what happens below ground is understandably hidden from view. But the importance of roots becomes obvious when corn crops face drought or severe weather.
The Goal Is To Help Farmers Benefit
For farmers, the significance of Hirsch’s work isn’t only about developing new hybrids. It’s about making sure breeders have enough genetic diversity to keep improving corn as growing conditions and production systems change.
The objective remains straightforward, she says: Identify germplasm with useful traits, understand how and why those traits perform under different conditions, and use that knowledge to give farmers better seed options.
You can hear more about Hirsch’s work in the latest episode of The Crop Science Podcast Show, available at the link below:
