Study Shows ‘Organic’ Wounds Improve Produce

Texas A&M AgriLife Research scientists have found benefits of insect leaf-wounding in fruit and vegetable production. Stress responses created in the fruits and vegetables initiated an increase in antioxidant compounds prior to harvest, the scientists say, which may make them healthier for human consumption.

“Many studies in the past supported this idea, but many others showed no differences,” said Luis Cisneros-Zevallos, AgriLife Research horticulture and food scientist in College Station and principal investigator for the study addressing this topic. “In our study we proved that wounding leaves in plants like those caused by insects produce healthier organic fruit.”

The research was recently published in Scientific Reports from Nature. It was conducted by an interdisciplinary team including molecular biologist Woo Young Bang and horticulturist Leonardo Lombardini, both former AgriLife Research scientists.

Cisneros-Zevallos said there was an existing idea proposed by others that insects present in the field in organic farming could cause a stress response in plants and increase antioxidant compounds. The hypothesis had never been tested until now, where the AgriLife Research scientists mimicked damage caused by insects.

“We conducted studies using strawberries as a crop model and applied various levels of wounding to the leaves a few days before harvesting the fruit,” said Facundo Ibanez an investigator for the project associated with the Instituto Nacional de Investigacion Agropecuaria, Uruguay. “We found how several genes associated with sugar translocation and phenolic compound biosynthesis were overexpressed in the distant strawberry fruit.”

All plants have the ability to respond to the environment by activating the secondary metabolism as part of a defense mechanism or an adaptation process. It also activates the primary metabolism, which will move the carbon source needed to produce those antioxidant compounds, Cisneros-Zevallos said.

“This research provides insight and understanding into the complexities of producing fruits and vegetables,” said Patrick Stover, vice chancellor and dean for the College of Agriculture and Life Sciences, Texas A&M AgriLife and director for Texas A&M AgriLife Research. “The future implications for this research are exciting and show how AgriLife researchers are working to improve plant production and nutrient quality for both producers and consumers.”

Ibanez said the study emphasized fresh produce as an excellent source of health-promoting compounds, and that perhaps insects in some way can be allies to achieve even healthier produce.

“Healthier grown produce for the food industry can be a driving force for large-scale production and an attractive investment to relevant stakeholders,” Ibanez said.

Organic farming in recent years has experienced continued growth and a higher demand among consumers. This has had a positive large-scale impact on the organic industry, farmers and other industries related to organic produce, Cisneros-Zevallos said.

“Our team has elucidated a controversy that was an open question for many years,” Cisneros-Zevallos said. “Understanding how these antioxidants are produced by a simple stress like wounding can certainly transform the way the fresh produce industry operates, including both organic and conventional. And it may allow the industry to adopt novel tools based on pre-harvest stress to favor the accumulation of healthier antioxidants in fresh produce and processed foods.”

After studies published in the past focused on post-harvest wounding stress effects on different crops, the team was inspired to apply the approach to leaf surfaces in the field to mimic the attack of insects on plants.

“This observation was key when we designed the strategies to be used in the study, that simple wounding stress on leaf surfaces elicited this systemic response with the unique observation of higher accumulation of phenolic antioxidants in fruit,” Ibanez said.