Exploiting pathogen defence trade-offs to manage risks of crop pest evolution against biocontrol agents

Abstract

Pathogens often exert strong selection on host populations, yet considerable genetic variation for resistance persists. Environmental heterogeneity may cause fitness trade-offs that help prevent fixation of pathogen resistance alleles in wild host populations. Pathogens are extensively used in biocontrol, yet the risks of pest resistance evolution are frequently underappreciated, and the key drivers of fitness trade-offs for pathogen resistance remain unclear, both in natural and managed populations. We investigate whether pathogen identity or host diet has a stronger effect on the fitness of resistance alleles by quantifying genetic variation and covariation for pathogen resistance in an insect pest across distinct pathogen and plant diet combinations. We demonstrate substantial heritability, indicating considerable risks of biopesticide resistance. Contrary to conventional thinking in host-pathogen biology, we found no strong genetic trade-offs for surviving exposure to two different fungal pathogen species. However, changes in plant diet dramatically altered selection, revealing diet-mediated genetic trade-offs affecting pest survival. Our data suggest that trade-offs in traits not strictly related to pathogen defence could nevertheless maintain genetic variation in natural and agricultural landscapes.