Data from: Effects of light quality on colonization of tomato roots by arbuscular mycorrhizal fungus (AMF) and implications for growth and defense

Beneficial soil microbes can enhance plant growth and defense, but the
extent to which this occurs depends on the availability of resources, such
as water and nutrients. However, relatively little is known about the role
of light quality, which is altered during shading, resulting in a low red:
far-red ratio (R:FR) of light. We examined how low R:FR light influences
arbuscular mycorrhizal fungus (AMF)-mediated changes in plant growth and
defense using Solanum lycopersicum (tomato) and the insect
herbivore Chrysodeixis chalcites. We also examined effects on
third trophic level interactions with the parasitoid Cotesia
marginiventris. Under low R:FR light, non-mycorrhizal plants activated the
shade avoidance syndrome (SAS), resulting in enhanced biomass production.
However, mycorrhizal inoculation decreased stem elongation in shaded
plants, thus counteracting the plant’s SAS response to shading.
Unexpectedly, activation of SAS under low R:FR light did not increase
plant susceptibility to the herbivore in either non-mycorrhizal or
mycorrhizal plants. AMF did not significantly affect survival or growth of
caterpillars and parasitoids but suppressed herbivore-induced expression
of jasmonic acid-signaled defenses genes under low R:FR light. These
results highlight the context-dependency of AMF effects on plant growth
and defense and the potentially adverse effects of AMF under shading.