Scientists applied solutions containing rose essential oil to the soil of potted tomato plants. jevelin / iStock / Getty Images Plus
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After a plant suffers an injury, metabolites called terpenoids are released to enhance its defenses. A new study led by scientists from Tokyo University of Science (TUS) has found that rose essential oil (REO) has the ability to stimulate defense genes in the leaves of tomato plants.
REO also attracts herbivore predators that protect plants from moths and mites. Because of these effects, the researchers concluded that REO can be effective as a sustainable organic pesticide.
“[O]ur study showed that rose essential oil (REO), rich in β-citronellol, played a crucial role in activating defense genes in tomato leaves. As a result, leaf damage caused by herbivores, such as Spodoptera litura and Tetranychus urticae, was significantly reduced,” the researchers wrote in the study. “Our findings suggest a practical approach to promote organic tomato production that encourages environmentally friendly and sustainable practices.”
Essential oils (EOs) derived from plants are used in cosmetics, detergents, food additives and pharmacology, a press release from TUS said.
The bioactivities of EOs have been shown to be exceptionally safe and to benefit human health. In addition, they have been found to induce neurotoxic effects in insects, causing a repellent response.
Plant EOs have an abundance of terpenoids that are able to control defense responses in plants by regulating the expression of their defense genes. When komatsuna and soybean plants are grown near mint, they show a marked improvement in their defense properties that make them resistant to herbivores. This happens through “eavesdropping” — a process during which the mint plant releases volatile compounds that trigger defense genes.
“Today, applying chemical pesticides is the method of choice for crop protection, but the damage they cause to the environment and ecosystems, along with the need to increase food productivity, stresses the need for safer alternatives,” the press release said. “Thus, there is an urgent need for investigation of plant defense potentiators. In this regard, the availability of EOs makes them attractive candidates as environmentally friendly plant defense activators.”
The lack of enough proven EOs to meet demand presents a challenge, however. To address this issue, the research team looked at tomato defense responses activated by 11 EOs.
“EOs used as fragrances for various purposes contain odor components, which may have the ability to work like volatile compounds in conferring pest resistance. We aimed to investigate the effects of these EOs on plants’ insect pest resistance,” said professor Gen-ichiro Arimura of the TUS Department of Biological Science and Technology in the press release.
The research team profiled how EOs enriched with terpenoid affected tomato plants. They applied solutions diluted with ethanol from 11 distinct EOs to potted tomato plant soil. After studying the leaf tissue’s gene expression through molecular analyses, they found that REO boosted the levels of plant defense genes PIR1 and PIN2.
The tomatoes treated with REO also showed less leaf damage from Spodoptera litura moth larvae and Tetranychus urticae mites.
The team also measured REO activity in a field experiment. They found 45.5 percent less damage from tomato pests than the control. The researchers feel REO could act as an effective pesticide alternative during winter and spring when there is less severe pest infestation. In addition, they think it could potentially lower pesticide use by nearly 50 percent during the summer.
“REO is rich in β-citronellol, a recognized insect repellent, which enhances REO’s efficacy. Owing to this, damage caused by the moth larvae and mites was significantly minimized, confirming REO as an effective biostimulant. The findings also showed that a low concentration of REO did not repel T. urticae but attracted Phytoseiulus persimilis, a predator of these spider mites, thus exhibiting a dual function of REO,” Arimura explained in the press release.
The study, “Novel Potential of Rose Essential Oil as a Powerful Plant Defense Potentiator,” was published in the Journal of Agricultural and Food Chemistry.
The study demonstrated the capacity of EO enriched with β-citronellol in turning on the defense genes of tomato leaves. It also showed that REO effectively enhances plant defense in a safe manner that does not leave toxic residue or result in phytotoxicity.
“Our study suggests a practical approach to promoting organic tomato production that encourages environmentally friendly and sustainable practices. This research may open doors for new organic farming systems. The dawn of potent environmentally friendly and natural pesticides is upon us,” Arimura said.
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