GERMANY – Dutch researchers from Delft University of Technology and Utrecht University have developed the first-ever method to monitor infections in plants in real-time, without the need to destroy them.

Delft scientists investigated downy mildew infections in lettuce, a plant species where such infections are typically only visible in their later stages. Plant scientists often don’t know how an infection progresses within a plant and what makes certain crops insensitive to pathogens.

“Until now, researchers had to kill a plant for each step in the process, stain it, and then examine it under a microscope,” said Jeroen Kalkman, associate professor in imaging physics. “Now, with this new imaging technique, we can track how a disease develops in a living plant in real-time.”

According to Jeroen Kalkman, associate professor in imaging physics, the new instrument provides insights, aiding in the cultivation of crops with broader resistance to various diseases.

He added that these crops require fewer pesticides, are better equipped to withstand extreme weather conditions, and ultimately yield much more.

The technique used is called dynamic optical coherence tomography (dOCT), which involves emitting light and measuring the time it takes for that light to reflect back, similar to ultrasound but with light instead of sound.

In just one and a half seconds, scientists can capture around 50 to 100 images of an infected lettuce leaf.

“We can effectively map plant diseases with dOCT because the pathogens move more than the plant cells. By assigning colours to areas with more movement, we can generate a strong contrast between the pathogen and the plant. “

Without dOCT, the disease would only be visible at a much later stage,” explained physicist Jos de Wit, who collaborated with biologists from Utrecht University for his doctoral research.

In addition to lettuce, the researchers have demonstrated that their instrument also works for other crops, such as radishes and peppers carrying parasitic roundworms.

However, further research is needed however to make this technique a user-friendly tool for biologists without a technical background.

The researchers noted that there are lettuce varieties that are resistant to downy mildew, but similar to the coronavirus, the disease continually evolves into new variants that can still infect resistant plants.

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