How Do Volatile Cues Impact Plant-Herbivore Interactions in Arabidopsis thaliana?
Plant-plant communication can provide information about environmental stressors such that plants prepare defenses against competitors or herbivores. By utilizing two genotypes of Arabidopsis thaliana we explored how emitter genotype impacted receiver plants in the context of herbivore cues. The effect of emitter genotype was observed on receiver plant fitness-related traits while grown alone, when grown in competition, and following herbivore damage. Additionally, the effect of pre-treated receiver plants on development and oviposition behavior of the specialist herbivore, Plutella xylostella, was monitored.
Plants grew 14 percent taller and produced 62 percent more fruits when indirectly exposed emitter plants with a different genotype. However, this response was repressed if herbivore damage cues were present. Receiver plants were 18 percent shorter and produced 45 percent less fruit on average when grown in competition, but the response to emitter treatment remained the same. We did detect an interaction between competitive treatments and emitter herbivore damage for total fruit set per pot. Pots with two Columbia ecotype plants produced 27 percent more fruit when emitters were undamaged compared to non-competitive pots when emitters were undamaged. Receiver plants grown in competition were more variable in their fruit production when exposed to undamaged plant volatiles. Emitter treatment did not elicit an effect on P. xylostella oviposition. Plutella xylostella raised on receivers pre-exposed to damaged plants spent slightly more time as pupa compared to those raised on receivers pre-exposed to undamaged plants. However, P. xylostella size did not differ as adults and emitter pre-treatment did not impact insect the amount of herbivore damage to receivers.
These results indicate that neighboring plants can indirectly increase plant yield despite planting density, which is a promising avenue for agricultural research aimed at closing the yield gap. The variability in yield between neighbors when competition was present indicates, though, that increased productivity may not be realized in high-density agricultural settings. We did not see feeding or oviposition deterrence of herbivores in response to priming treatments in this specialist herbivore. Therefore, the effects of volatiles should be explored in a variety of herbivores before implementing this means of crop protection.