Data from: Root inoculation with beneficial soil microbes enhances indirect plant defenses induced by insect feeding and egg deposition

Plants can respond to insect egg deposition by emitting
oviposition-induced plant volatiles (OIPVs) recruiting parasitoids. The
recruitment of carnivore insects in response to egg deposition is
considered an indirect defense strategy that is widespread in the plant
kingdom. In recent years, there has been increasing evidence showing that
microbial colonization can influence the strength of plant responses to
insect herbivory, yet no information is available on how beneficial
microbes modulate indirect defenses induced by insect egg deposition. In
this work, we evaluated the effects of inoculation with the beneficial
soil fungus Trichoderma harzianum strain T22 on a tritrophic system
consisting of tomato, the southern green stink bug Nezara viridula and its
associated egg parasitoid Trissolcus basalis. We used Y-tube olfactometer
assays to evaluate the behavioral responses of the parasitoids to OIPVs
emitted by plants colonized with beneficial soil microbes. We also used
gas chromatography coupled with mass spectrometry (GC-MS) to investigate
how root inoculation with T. harzianum T22 affects the chemical
composition of induced plant volatiles. 3. In olfactometer assays, we
found that root inoculation with T. harzianum T22 enhanced the attraction
of the egg parasitoid towards tomato plants induced by N. viridula feeding
and oviposition activities. In particular, the egg parasitoid preferred
OIPVs emitted by tomato plants previously inoculated with T. harzianum T22
over OIPVs emitted by non-inoculated plants. Furthermore, chemical
analysis showed that root inoculation with T. harzianum T22 resulted in
changes in the composition of OIPVs, which was consistent with the
behavioral observations. Among the compounds that strongly contribute to
the chemical differences between OIPVs from non-inoculated and inoculated
plants, chemical analysis identified green leaf volatiles
((Z)-3-hepten-1-ol, (E,E)-2,4-hexadienal), along with terpenoids (terpinen
4-ol, α-tujene and δ-elemene). 4. Taken together our results indicate that
beneficial soil microbes enhance indirect plant defenses induced by
feeding and oviposition, broadening our understanding of plant responses
to insect eggs. Our results underscore the importance of taking into
account the role of microorganisms to fully comprehend the intricate
interactions among plants, herbivore eggs and their associated egg
parasitoids.