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

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.

Keywords: Epichloë; Erebidae; alkaloids; detoxification; fungus; native herbivore.

Figure 1

Leaf area consumed from the seven experimental lines and two cultivars of ryegrass by C. rudis in a no-choice test. Different letters indicate significant differences according to Tukey’s test (p ≤ 0.05). The data correspond to the mean with its corresponding standard error.

Figure 2

Survival rate for C. rudis larvae feeding on leaves of JUMBO (E−) subjected to several doses of peramine. Different letters indicate significant differences (p ≤ 0.05) based on ANOVA test following by Tukey’s test.