Volatile cues of enhanced attractiveness to Parapanteles hyposidrae (Wilkinson) wasps mediated by jasmonic and salicylic acid pathways synergism in tea plant.

Background: The jasmonic acid (JA) and salicylic acid (SA) pathways are often thought to interact antagonistically in plants when mediating anti-herbivore resistance. However, we previously found that the two pathways in tea plant interact synergistically when treated with 1.5 mmol/L methyl jasmonate (MeJA) and 20 mmol/L SA at 12 h intervals (MeJA+SA treatment). Here, we investigated how and why JA-SA synergism in tea plants affected chemotaxis of Parapanteles hyposidrae (Wilkinson) wasps, the parasite of tea geometers.

Results: Wasp attractiveness of MeJA+SA-treated plants was 1.3-fold higher than MeJA-treated plants, although SA-treated plants could not attract more wasps. Five attractive compounds, including (Z)-3-hexenyl acetate, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), indole and (E,E)-α-farnesene, were emitted more by MeJA+SA-treated than MeJA-treated plants. Based on the difference in volatiles induced by MeJA and MeJA+SA treatments, five attractive components were separately added to artificial MeJA-induced volatiles (MV) or taken out from artificial MeJA+SA-induced volatiles (MSV). The attractiveness of MV to wasps was enhanced when DMNT or indole was added, whereas the attractiveness of MSV decreased when DMNT, indole or linalool was taken out. When DMNT and indole were both added into MV, the attractiveness of volatile blend to wasps became similar to MSV.

Conclusion: Increased DMNT and indole emissions are the key cues causing volatiles mediated by JA-SA synergism to be more attractive to P. hyposidrae wasps than those mediated by JA pathway alone. This provides new insights into the phytohormone pathway networks in tea plants and the development of natural enemy attractants. © 2025 Society of Chemical Industry.