Kansas State University Researchers Find New Pathogens in Soybean Seeds

Mid-season soybean field. ©Debra L Ferguson Stock Photography

A single seed seems so simple. Put it in the ground, give it some care, and you’ve soon grown food.

But Chris Little knows better. It’s why he’s spent the better part of the last six years learning more about the not-so-modest beginnings of soybean seeds in Kansas.

“Seeds have microorganisms that live on and within them,” said Little, an associate professor of plant pathology at Kansas State University. “Some of those seed-borne microorganisms are harmless and actually helpful to the seed. But pathogens also reside within the seeds.”

Since 2011, Little has been studying the biology of soybean seeds to find out what affects their ability to germinate and, thus, impact a farmer’s productivity. Pathogens, such as viruses, bacteria or other microorganisms, cause disease and thus rob farmers of greater crop yields.

“You can find a lot of different pathogens, a lot of different fungi, a lot of organisms that live in the seed and seedlings, but the question becomes are they actually pathogens” capable of causing disease, Little said.

Little and his research team have collected soybean seeds from 11 locations in Kansas, which he says includes “several hundred samples.” Then they isolated the fungi in the laboratory to see just what’s living inside the seeds.

“The way we categorize pathogens has changed, so being able to identify what it is – in a precise way – helps us to figure out control strategies,” he said. “If we don’t know the perpetrator, we can’t solve the crime. So there’s a lot to this project in figuring out who the perpetrators are in a better way.”

The researchers had a recent breakthrough when they discovered that two fungi – Fusasrium thapsinum and Fusarium fujikoroi – pathogens of sorghum and rice – are present in soybean seeds in Kansas.

Using advanced sequencing techniques that essentially extract DNA from the seed, the researchers discovered that Fusarium fungi are present in 100 percent of the seed samples they gathered. And, Little noted, “many of these seed-borne pathogens may cause seedling problems.”

Their finding is significant because both species, and many more, are capable of being pathogens and are resistant to fungicides commonly used to treat seed.

“It raises big questions,” Little said. “Just because you can detect it, what are you going to do about it?”

So far, there’s not a good answer to that question, but researchers now have a better view of pathogens that affect soybean seeds and seedlings. They can determine the best seed treatments or fungicides to use to control for disease, or provide DNA information that helps plant breeders develop stronger varieties.

“There’s always new germplasm that needs to be screened for resistance to make sure that you’ve got really good, well-adapted varieties,” Little said. “For Kansas, we want varieties that have good drought tolerance, and we want good environmental-stress tolerance. We also want to have soybean cyst nematode resistance and sudden-death syndrome resistance, and it would also be good if we had good seedling health with those too.

“There’s kind of a package that you want to put together, and this study feeds into that package.”

The research was primarily funded by the United Soybean Board and the North Central Soybean Research program, which has funded work in several midwestern states. The Kansas Soybean Commission also provided support for the project.

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