Corn one step closer to bacterial leaf streak resistance

Sep 16, 2019

By Lauren Quinn

Bacterial leaf streak, a foliar disease in corn, has only been in the United States for a handful of years, but Tiffany Jamann says it's a major problem in the Western Corn Belt.

"We don't have hard numbers yet, but this pathogen in other systems can cause up to 20% yield losses," says Jamann, an assistant professor in the Department of Crop Sciences at the University of Illinois and co-author of a new study in the journal Crop Science. "There's no effective chemical control. Fungicides don't work, as it's a bacterial disease. That's why host resistance is going to be critical, just as it is for controlling other bacterial diseases of corn, such as Goss's wilt and blight."

The disease-causing bacteria squirm in through open pores—stomata—on the leaf surface, then set up shop between veins to form long greyish streaks. Although no one has determined precisely what's happening inside the plant, Jamann says the necrotic lesions are disrupting the photosynthetic capacity of the leaf. And that hurts yield.

To make matters worse, bacterial leaf streak looks similar to a fungal disease of corn, gray leaf spot. Farmers may confuse the two diseases and spray fungicide, which is not only ineffective, it's an unnecessary cost.

Currently, there is no chemical control agent for bacterial leaf streak, and no completely resistant corn hybrids exist. But, in the Crop Science study, Jamann and her collaborators make a promising discovery that could lead to resistant lines in the future.

By inoculating 26 diverse corn lines with the disease and selecting promising lines for further analysis, they found corn varieties with moderate resistance and genetic regions associated with increased levels of resistance.

"Although we didn't identify any large-effect resistance genes, the study is the first report of host resistance to bacterial leaf streak that has ever been published," Jamann notes.

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Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.