It turns out being dysfunctional isn't always a bad thing -- at least in the soybean world. Researchers are finding a new and unexpected way to tackle soybean cyst nematode (SCN) by introducing a "dysfunctional" or a bad copy of a resistance gene.
There's some complex genetic gymnastics going on here. A gene known as GmSNAP02 has been a known component of several types of native resistance deployed to protect soybean varieties from SCN. Only recently have scientists begun to understand that the gene may be helping SCN overcome genetic resistance mechanisms in the soybean plant. Now there's hope manipulating GmSNAP02 might deliver a sucker punch to preserve the utility of varietal resistance in soybeans.
"Think of it like a lock-and-key model, where SCN is the key and GmSNAP02 is the lock," explains Melissa Mitchum, professor in the College of Agricultural & Environmental Sciences at the University of Georgia and a member of the research team that made the discovery. "If you get rid of that lock, the nematode can't access the plant. You make the parasite ineffective."
SHORING UP PEKING
Farmers have relied on PI 88788 genetic resistance in soybean varieties for decades, but overuse has eroded the utility of the tool. Read more here: https://www.thescncoalition.com/… .
Consequently, there's an urgency for alternative modes of resistance to be rotated with PI 88788 to control SCN populations. Peking-based resistance, which contains three genes, has become the new tool of choice, although commercial soybean varieties containing it remain limited.
This new research shows nematodes can reproduce on Peking genetic resistance and appear to be doing it by exploiting GmSNAP02. In a recent release from The SCN Coalition, Mitchum explained it is now believed some types of resistance work better than others because they lose this GmSNAP02 protein, circumventing the nematodes and making the plant more resistant.
The fact that Peking resistance contains three genes is critical in the nematode battle, said Andrew Scaboo, assistant professor in the Division of Plant Science and Technology at the University of Missouri, who is spearheading the project with Mitchum.
However, if farmers use Peking exclusively, nematodes will develop resistance. "This is where this fourth gene comes into play. Adding a nonfunctioning copy of GmSNAP02 enhances the nematode resistance of Peking," Scaboo said. "If we can come up with a strategy now for using this and other genes in rotation, we could avoid a repeat of the situation we now have with PI 88788."
A quadruple stack would enhance the genetic diversity on the market, which is critical to long-term management of SCN. "As we bring different modes of action into the rotation, we enhance the durability of all the tools in our toolbox," Mitchum explained.
Scaboo is a year into a roughly three-year process developing the plant material needed to test whether the GmSNAP02 omission impacts yield. That question must be answered before the new resistance tool can be moved toward commercialization.
"Nearly every major company and some of the smaller ones have reached out and set up meetings since the report on the discovery (https://www.nature.com/…) was published," Scaboo said. "That signals they know SCN is a big problem for farmers." Private breeders account for over 90% of U.S. soybean varieties.
The fact that CRISPR gene editing can be used to "knock out" GmSNAP02 is an advantage -- especially for breeders working with a Peking background, according to the scientists. "CRISPR technology facilitates and speeds along the breeding process for forging this stack," Scaboo said.
Private soybean companies are invested in the longevity of their soybean varieties. "One way to give products longevity is with better control of pathogens," Scaboo said. "With GmSNAP02, the private sector can pursue prescriptive management strategies for pathogens like SCN. The resistance this gene provides has the potential not only to protect soybeans and raise yield, but also to manage SCN long term."
DISCOVERY PAVES WAY
The knowledge gained from this discovery is also important. "The fact you could knock out a gene in a resistant background and gain more resistance was unexpected," Mitchum said.
"Looking ahead, we want to understand how the nematode may be targeting GmSNAP02," Mitchum said. "Hopefully, that understanding will give insight into how we can further enhance durability of the tools in our toolbox and add to it."
Advances in technology are also shifting the conversation on SCN management. "We are starting to understand the genetic architecture on a level that the resistance source is becoming irrelevant," Scaboo said. "It would be great for seed companies, farmers and the industry to start talking about these resistance genes rather than sources like Peking or PI 88788."
The GmSNAP02 project started with a plant breeder (Scaboo) and a nematologist (Mitchum) who set out to map the genetic architecture of known sources of SCN resistance. Four years of interdisciplinary research involved professors, research staff and students. It was funded by farmer-supplied checkoff dollars by way of the Missouri Soybean Merchandising Council, the North Central Soybean Research Program, and the United Soybean Board. The National Science Foundation-National Institute of Food and Agriculture provided additional grant funding. The next steps -- getting this new mode of resistance to farmers -- will require investment from the private sector and an all-hands-on-deck approach to drum up awareness.
"All those people, industries and perspectives are what made this happen," Scaboo said. "That public/private collaboration is so important when it comes to delivering new tools like GmSNAP02 that better equip farmers to manage SCN."
Find the entire release and learn more about SCN and what's being done to fight it at thescncoalition.com.
For another look at the research go to: https://mosoy.org/…
For a DTN article on an upcoming genetically engineered trait from BASF that will stack with other resistance https://www.dtnpf.com/…
Pamela Smith can be reached at firstname.lastname@example.org
Follow her on X, formerly known as Twitter, @PamSmithDTN
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