Systemic defense induced by fatty acid compounds from marine macroalgae, Chaetomorpha antennina in tomato (Solanum lycopersicum) plants alters the susceptibility of the polyphagous agricultural pest, Spodoptera litura Fab

Abstract

Background Seaweeds contain a widespread range of fatty acids (FA), and several of them have potential bioactivity. FAs are dynamic members of all biota, as well as being acknowledged for their critical function in initiating phytohormone interactions and acting as important participants in many defence signalling pathways of the plant system. The current study looks at the defense-eliciting potentials of fatty acids from the green seaweed Chaetomorpha antennina and their impact on the polyphagous insect pest Spodoptera litura (Fab). Results The seaweed was detected with 19 fatty acids, with larger proportion of hexa and octadecanoic and linoleic acids. The algal fatty acid compounds (CFA) was successful in eliciting salicylic acid and phenolic compounds biosynthesis along with enzymes peroxidase (PO) and polyphenol oxidase (PPO). The defense enzymes and phenol levels increased post infestation with S. litura. CFA was also effective in causing direct mortalities to the larvae (II-V instars). S. litura larvae exposed to elicited tomato plants were severely affected physiologically and morphologically, displaying visible aberrations as well as morphogenetic defects such as altered larval-pupal duration and biomass. Reproductive performances of adults were also severely affected. Decrease in food utilization, nutritional indices with a corresponding decrease in phosphatase and gut enzymes affirm feeding deterrence of the larvae, which was endorsed by histological analysis of midgut cell disruption of exposed larvae. Detoxification enzyme levels of exposed larvae denote the inability of larval immune system to evade harmfulness of CFA. Conclusion Hence, the study finally confirms the elicitor potentials of fatty acid compounds from C. antennina, by inducing natural systemic defences. This investigation unlocks novel forecasts besides delivering an unconventional method for crop protection to moderate or interchange the solicitation of chemical pesticides.