# A Countermeasure Strategy against Peramine Developed by Chilesia rudis in the Endophyte–Ryegrass–Herbivore Model

## TL;DR

This study explores how a Chilean larva adapts to toxic compounds in ryegrass infected with endophytic fungi.

## Contribution

The study reveals that Chilesia rudis larvae can adapt to peramine, a toxic alkaloid, through counter-adaptation mechanisms.

## Key findings

- Chilesia rudis larvae prefer certain ryegrass cultivars and show variable pupal development times.
- Peramine was detected in larval bodies, suggesting adaptation to the toxin.
- Adult wing lengths varied across ryegrass cultivars, indicating performance differences.

## Abstract

Exploitation of the symbiotic relationship between endophytic fungi and ryegrass is a crucial technique for reducing the incidence of insect pests. This is primarily due to the production of alkaloids, such as peramine, by the fungi. This alkaloid has been reported as both a deterrent and toxic to a variety of insects. However, insects have developed various strategies to counteract plant defenses. One of the most studied methods is their ability to sequester toxic compounds from plants. In this study, we examined the feeding preferences and adaptation to peramine in Chilesia rudis, a native Chilean larva. Using a no-choice assay, we assessed larval feeding preferences and mass gain on seven experimental lines and two commercial cultivars of endophyte-infected and non-infected ryegrass. Pupal development time and adult performance were evaluated post-assay. Additionally, we measured peramine content in larval carcasses, feces, and ryegrass leaves. Jumbo was the most preferred cultivar with 32 mm2 of leaf tissues consumed. The longest pupal development time was observed in L161 and ALTO AR1, both at 28 days. Wing length in adults was greatest in the Jumbo and L163 cultivars, measuring 1.25 cm and 1.32 cm, respectively. Peramine concentrations were detected in the bodies of C. rudis. In conclusion, this larva can adapt to endophyte-infected ryegrass and develop counter-adaptation mechanisms to mitigate the effects of peramine.