D3078: (1st Place) Salival of the spittest: Origin of phytohormones in fall armyworm saliva

The fall armyworm (Spodoptera frugiperda) is a generalist herbivore and serious crop pest across the globe. Recently, larvae of this species were found to contain plant hormones in their saliva; these phytohormones are capable of altering plant defense responses normally induced by herbivory. The phytohormones found at the highest concentrations in fall armyworm larvae include benzoic acid, salicylic acid, and indoleacetic acid. We hypothesize that these compounds are found in saliva due to one or a combination of three possible sources: sequestration from ingested food, synthesis by the caterpillar, or synthesis by larval gut microbes. S. frugiperda larvae were fed artificial diet containing high levels of each phytohormone. To observe the effect of the microbiome, half of these larvae were reared axenically while the rest had intact microbiomes. After growing to the sixth instar, salivary glands were dissected out of larvae and analyzed for phytohormone concentration using GC-MS. Our results indicate that S. frugiperda larvae are capable of sequestering all three phytohormones of interest from food sources. Preliminary findings suggest that gut microbes may improve sequestration of salicylic acid, but further research will be conducted to elucidate the precise effect of the microbiome.