Many people enjoy a cup of tea, yet few know the constant pressure tea plants face out in the field. One of their most damaging pests is the grey tea geometrid ( Ectropis grisescens ). Left unchecked, these hungry caterpillars can defoliate entire tea plantations. Farmers traditionally rely on chemical pesticides to protect harvests — but this is not a sustainable long-term fix.
What if we could boost tea plants’ own natural defenses? Scientists are turning to an unexpected ally: soil microbes.
Arbuscular mycorrhizal fungi (AMF) are widespread soil fungi that form symbiotic partnerships with the roots of most land plants. Previous work has shown they help plants take up nutrients, but it remained unclear whether AMF could help tea plants fend off insect pests — and crucially, what molecular mechanisms drive that protection.
Wenxu Lian and colleagues at the Tea Research Institute, Anhui Academy of Agricultural Sciences, set out to answer that question. The team grew “Wancha No. 4” tea seedlings, inoculating half with Rhizophagus intraradices , a common AMF species, then let grey tea geometrid caterpillars feed on the plants. Their results were recently published in Microbiology China .
The findings were striking. Caterpillars feeding on mycorrhizal tea seedlings gained far less weight than those feeding on seedlings without the fungal partner. In short, the underground fungus was helping tea plants fight aboveground herbivores.
“It works much like pre-vaccination,” said Wenxu Lian, first author of the study. “Once the fungus colonizes the roots, it primes the tea plant. It tunes key genes in the jasmonic acid pathway, keeping the plant primed and ready to defend itself.”
Jasmonic acid is a core plant defense hormone. The team observed that AMF-inoculated tea seedlings mounted a much faster response when caterpillars began feeding. Levels of defensive enzymes including lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL) quickly spiked in leaves. When bitten, the plant rapidly cranks up production of defensive compounds to deter insect feeding.
Correlation analysis further confirmed that the activity of key genes in the jasmonic acid pathway directly predicted how much weight the caterpillars gained — this is the core mechanism behind the fungal protection.
The team sees clear potential for real-world green pest management. “Down the line, we could formulate this beneficial fungus into a biofertilizer to mix into soil when tea seedlings are planted. Better-defended young tea plants would need fewer chemical pesticides,” Lian explained.
This is only an early step, however. Lian’s group plans to add more sampling time points in follow-up experiments, to map exactly how this defensive “warning system” behaves across different stages of pest attack.
10.13344/j.microbiol.china.260002
Response of endogenous jasmonic acid in mycorrhizal tea seedlings to infestation by Ectropis grisescens larvae
20-Oct-2026