Raman spectroscopy delivers fast, accurate monitoring of peanut plant health

27 May 2020

Texas A&M AgriLife scientists using new approach to biophysics to accelerate breeding of high-quality, high-yield nuts.

The usually lengthy process of breeding better peanut plants can be accelerated by using Raman spectroscopy. Texas A&M AgriLife biophysicists and plant breeders have demonstrated the use of Raman spectroscopy to quickly scan the levels of oleic acid in peanuts. Oleic acid, a monounsaturated oil, lends peanuts a longer shelf life. The oil is also healthy for the heart.

As the largest comprehensive agriculture program nationally, Texas A&M AgriLife brings together a college and four state agencies focused on agriculture and life sciences within The Texas A&M University System.

The scientists have also used this method to determine how resistant plants are to nematode pests. Using Raman spectroscopy is quicker, cheaper and more portable than standard approaches of screening peanut varieties for these beneficial traits. The work has been published in Nature’s Scientific Reports.

“We’ve shown that the method can save a huge amount of time in our screening process,” said John Cason, Ph.D., coauthor and Texas A&M AgriLife Research peanut breeder, Stephenville. “You can get a ‘fingerprint’ of a particular peanut and tease out large amounts of information. The possibilities are endless.”

“Raman spectroscopy is commonplace in biochemistry but mostly unknown in the world of farmers and plant breeders,” said Dmitry Kurouski, Ph.D., principal investigator of the study and assistant professor in the Department of Biochemistry and Biophysics, Texas A&M College of Agriculture and Life Sciences. “Yet it is portable, inexpensive, accurate and fast, and can transform digital farming.”

Funding for the study came from AgriLife Research and the Governor’s University Research Initiative. In addition, the Texas Peanut Producers Board and Southwestern Peanut Shellers Association provided funding for Cason’s group to buy a hand-held Raman spectrometer.

Benefits of Raman methods

Previously, if Cason wanted to analyze the pest-resistance of plants or the fatty acid content of peanuts, he would extract DNA from plants or send samples to an off-site lab for infrared analysis. Both methods are considerably more time-, cost- and labor-intensive than Raman, he said.

For this project, the collaborators used a commercially available, hand-held Raman spectrometer, a device about the size of a shoebox. Raman spectroscopy measures how materials scatter harmless laser light. Each material has a specific scattering characteristic that offers clues about many types of molecular information in a one-second scan. Running a scan is relatively straightforward, Cason said, but the collaborators are still developing and fine-tuning ways to analyze the data.

Cason’s team received training and guidance from Kurouski and three young scientists from his lab: Charles Farber, a graduate student; Lee Sanchez, a research assistant; and Stanislav Rizevsky, Ph.D., a visiting scholar.

Scans of peanut leaves could distinguish nematode-resistant and susceptible plants with roughly 75% accuracy. What’s more, scans of peanut seeds could distinguish with 82% accuracy the varieties with high levels of oleic acid.

Working for peanuts

The team is currently expanding its studies of peanut plants. The first goal is to use Raman to quickly isolate peanut varieties with high tolerance for drought conditions. The team is also looking into expanding its studies of nutritional content to help breed more nutritious peanut varieties.

One limitation of the technology is that the scanner needs to be in close contact with the material being scanned. Kurouski’s team is now working on a Raman “telescope” to enable scans of plants that are 30 meters (100 feet) distant. “Biophysicists and peanut breeders don’t usually associate in the same circles, but this has been a good project,” Cason said. “I don’t think it will be the last from this team.”