Nayelly Rangel, a graduate student at Texas Tech University, will present the team’s results at the spring meeting of the American Chemical Society (ACS). ACS Spring 2025 is being held March 23-27; it features about 12,000 presentations on a range of science topics.
“Powdery mildew is one of the most contagious diseases that affects grapevine plants,” says Rangel. “It reduces plant growth, fruit quality and quantity, and it can lead to a decline in wine quality.”
The current method to identify an infection relies on humans looking for tell-tale patches of grey powder along plant leaves. But, by then, the condition is usually serious and requires large amounts of fungicide to eradicate. Past research showed that dogs can identify powdery mildew by smell. But not much is known about the chemistry of what these animals smell, or whether the plants’ odor profile changes as the infection progresses.
“Our four-legged friends don’t talk, so we’re trying to understand what they are encountering when they’re sniffing,” says Paola Prada-Tiedemann, a professor of forensic science at Texas Tech University who is leading the study. So, the researchers set out to identify which volatile organic compounds, or airborne scents, grapevine leaves give off at different stages of powdery mildew infection.
First, the team needed a technique that would keep leaf samples intact for dog training. So, they placed a leaf inside a vial and inserted a tiny absorptive fiber into the vial to pick up chemicals from the air above a leaf. From there, the researchers characterized the volatile organic compounds (VOCs) stuck to the fiber by inserting it directly into a gas chromatograph-mass spectrometer.
“Our approach is unique because we’re testing the exact location where a canine sniffs the grape leaf,” says Rangel. “So, we’re analyzing the same airspace in both scenarios, whether we’re in the chemistry lab or the canine lab.”
So far, the team has optimized their process from the VOCs emitted from healthy leaves. Initial results from comparisons of healthy and fungus-impacted grapes revealed that the baseline odors emitted from healthy leaves include more acidic odor compounds than sick ones. In fact, healthy leaves released fewer vapors over time, says Rangel, in contrast to sick leaves that expelled more VOCs as the infection grew.
Next, the researchers will analyze the chemical composition of what’s wafting off the leaves at different stages of infection. Once they’ve identified a few key molecules, they will present each one individually to the canines, measure the animals’ responses to each, and test the smallest amount needed for detection. Like how certain scents, such as vinegar’s, are strong in small amounts, the researchers think that dogs may pick up on certain VOCs more easily than others. Using those compounds for training could enable more sensitive and accurate mildew identification, especially early-stage infections.
“The ultimate goal is to move away from the visual diagnosis of mildew to odor diagnosis as the gold standard,” says Prada-Tiedemann. “Even when we can’t see it ourselves, the dog sitting next to a plant can tell you with their nose, ‘uh oh, that vine’s starting to go.’”
By “bridging the canine to chemistry,” as Prada-Tiedemann says, the team wants to find a more efficient solution for protecting grapevines from a widespread and damaging disease. After all, she adds, “We all want good wine!”
The researchers report no external funding for this work.
A Headline Science YouTube Short about this topic will be posted on Sunday, March 23. Reporters can access the video during the embargo period, and once the embargo is lifted the same URL will allow the public to access the content. Visit the ACS Spring 2025 program to learn more about this presentation, “Evaluating chemical odor profiles of Vitis vinifera: Odor profiling for pathogen identification” and other science presentations.
###
The American Chemical Society (ACS) is a nonprofit organization founded in 1876 and chartered by the U.S. Congress. ACS is committed to improving all lives through the transforming power of chemistry. Its mission is to advance scientific knowledge, empower a global community and champion scientific integrity, and its vision is a world built on science. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, e-books and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.
Registered journalists can subscribe to the ACS journalist news portal on EurekAlert! to access embargoed and public science press releases. For media inquiries, contact newsroom@acs.org.
Note to journalists: Please report that this research was presented at a meeting of the American Chemical Society. ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.
Follow us: Facebook | LinkedIn | Instagram
Title
Evaluating chemical odor profiles of Vitis vinifera: Odor profiling for pathogen identification
Abstract
Powdery mildew is a highly contagious fungal disease that can target a wide variety of plants. Though this disease is rarely fatal, it can severely weaken the plant, reduce growth and fruit yield, and increase susceptibility to other diseases. This pathogen has risen in importance to viticulturists due to its impact on vineyards economy and fruit quality. There is an increasing need to develop more precise methods of disease identification to enhance current mitigation strategies. One such method involves the use of detection dogs. Biological detection dog training must adequately reflect what canines will encounter in the field, and to do so, research must be conducted not just to optimize training methods but to also understand the target odor source composition. Therefore, the goal of this research is to identify grapevine powdery mildew specific volatile organic compounds (VOCs) through the headspace analysis of healthy and infected plant leaves using solid-phase microextraction/gas chromatography-mass spectrometry. Targeted method parameters for headspace diagnostic applications included the optimization of the SPME fiber and extraction time to determine maximum extraction efficiency. Evaluating the VOC profiles of grape leaves as the infection progresses gives insight on characteristic volatile biomarkers, which can aid in canine detection training by providing an objective volatolomic approach on pathogen identification.
END
