Larval antibiosis to cabbage stem flea beetle ( Psylliodes chrysocephala ) is absent within oilseed rape ( Brassica napus )

Abstract

BACKGROUND Insect pests present a global threat to crops, with plant resistance representing a key breeding goal. The cabbage stem flea beetle ( Psylliodes chrysocephala ; CSFB) is a key pest of oilseed rape ( Brassica napus ; OSR) within Europe; however, CSFB resistance is yet to be found within B. napus . To address this, we examine CSFB larval development over time, explore antibiosis across a genetically diverse B. napus panel, and test whether larvae can develop within model Brassicaceae species ( Brassica rapa and Arabidopsis thaliana ). RESULTS CSFB larvae completed development from four-weeks post-infestation, undergoing a 20-fold size increase, with larval recovery after two weeks allowing semi-high throughput resistance phenotyping. Applying this method to 98 Brassicaceae genotypes (97 B. napus and a single Sinapis alba ), we found weak evidence for genotype effects on larval survival. However, phenotype validation with ‘resistant’ and ‘susceptible’ B. napus genotypes showed no differences in larval survival or adult emergence. Larval antibiosis was consistently observed in S. alba . Finally, we showed that model B. rapa and A. thaliana genotypes represent suitable hosts for CSFB, with larvae increasing 8-10× in size after two weeks. CONCLUSION CSFB larval antibiosis appears absent within B. napus , possibly due to bottlenecks experienced during domestication. However, larval antibiosis is present within S. alba , and future work should study the basis of this resistance. Further, CSFB larval screening in Brassicaceae model species presents an opportunity to explore CSFB resistance genetics, informing breeding progress for insect resistance in B. napus .

Code and data availability

The paper states that all data and code for its CSFB larval antibiosis phenotyping analyses are deposited on Zenodo (DOI: 10.5281/zenodo.18009385), and a methods protocol is deposited separately (10.5281/zenodo.18009476). These are paper-specific, public assets; however, no Zenodo URL appears in the allowed_urls list,

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