Breeding Pushes Disease Tolerance Envelope

07:00AM Jul 17, 2018
Corn 09
Breeders are advancing disease tolerance in corn and soybeans.
( Aimee Cope )

Breeding advances brought an era of advanced disease control. The future of disease tolerance will use advanced breeding with targeted approaches that help maximize corn and soybean yield potential.

“The top five diseases in corn we focus on are anthracnose stalk rot, gray leaf spot, Northern corn leaf blight, Goss’s wilt and Southern rust,” says Jared Webb, DeKalb product development manager. 

In soybeans, breeders focus on: white mold, phytophthora, sudden death syndrome and frogeye leaf spot.

“Disease tolerance is something we pay close attention to and select for,” says Shane Meis, Wyffels Hybrids director of research. “But we have to make sure yield isn’t sacrificed for disease tolerance. That perfect mix is the genetics that maintain high yield and have disease tolerance.”

Corn and soybean breeding advances result in a 1% to 2% yield gain each year—and at least part of that can be attributed to enhanced disease tolerance. While there still is a considerable number of crosses performed at random and then evaluated for performance, molecular markers, double haploid breeding and advanced gene editing speed the process at which advances are made and go to market.

“Today we still do traditional testing, but we really look at it from a molecular level,” says Kevin Cavanaugh, Beck’s Hybrids director of research. “We use molecular markers that are associated with resistance to certain diseases to screen parent lines. Most corn breeding programs use marker programs.”

Say you live in an area with high risk for gray leaf spot, researchers can use what they know about the corn genome to see if an inbred (single parent line) has natural resistance. If it does, and they’re breeding for your geography, they’ll keep that parent in the mix to make sure you have a certain level of disease resistance.

“One thing that’s really helped to identify and maintain resistance is double haploid breeding,” Meis says. “We’re testing with something that is fully inbred, genetically fixed, which means resistance will definitely occur in subsequent generations.”

Traditional breeding can identify resistance but lose it the following generation during the inbreeding process because resistance wasn’t genetically fixed. Double haploids don’t change from one generation to the next, so resistance will be present in the plant every time.

Finally, the most futuristic of breeding possibilities, gene editing programs such as CRISPR, could help bring products to market faster and with fewer regulatory hurdles. This technology allows researchers to make quick, efficient, GMO or non-GMO (depending on their goal) changes to the genome. It essentially involves inserting desirable or deleting undesirable parts of the genome.

“There are so many possibilities in gene editing, and we’re trying to leverage those,” Webb says. “The breeding cycle can take up to eight years though, so we have a few years before we’ll see the fruits of those efforts.”

As a result, traditional breeding for disease tolerance is still important. “We do 950,000 genetically unique soybean line tests each year because you have to look at a large number to see the best yield advances,” says David Thompson, Stine Seed national marketing and sales director. “With that number of products you’ll find solutions for diseases and other issues, without sacrificing yield potential.”

As disease tolerance improves, yield potential will only increase. Take a look at each of your fields and select hybrids or varieties that fit your disease pressure to maximize yield, while minimizing some of the need for added costs such as fungicide.