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要旨:
Plants release complex volatile blends after separate attack by herbivores and pathogens,
which play many roles in interactions with other organisms. Large perennials are often
attacked by multiple enemies, but the effect of combined attacks on volatile emission is rarely
studied, particularly in trees.
We infested Populus nigra trees with a pathogen, the rust fungus Melampsora laricipopulina,
and Lymantria dispar caterpillars alone and in combination. We investigated poplar
volatile emission and its regulation, as well as the behavior of the caterpillars towards volatiles
from rust-infected and uninfected trees.
Both the rust fungus and the caterpillars alone induced volatile emission from poplar trees.
However, the herbivore-induced volatile emission was significantly reduced when trees were
under combined attack by the herbivore and the fungus. Herbivory induced terpene synthase
transcripts as well as jasmonate concentrations, but these increases were suppressed when
the tree was additionally infected with rust. Caterpillars preferred volatiles from rust-infected
over uninfected trees.
Our results suggest a defense hormone crosstalk upon combined herbivore–pathogen
attack in poplar trees which results in lowered emission of herbivore-induced volatiles. This
influences the preference of herbivores, and might have other far-reaching consequences for the insect and pathogen communities in natural poplar forests.
