Exploring White Mustard Variety for Novel Cabbage Stem Flea Beetle Resistance.

Gill, Susannah Elizabeth (2025) Exploring White Mustard Variety for Novel Cabbage Stem Flea Beetle Resistance. Doctoral thesis, University of East Anglia.

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Abstract

The Cabbage Stem Flea Beetle (CSFB, Psylliodes chrysocephala L.) is the most significant insect pest of oilseed rape (OSR, Brassica napus L.), causing major yield reductions, particularly in the UK and mainland Europe. Years of commercial breeding focussed on yield and quality traits has resulted in a trade-off in the ability of crops to withstand biotic threats. This, paired with the limited use of chemical controls, has left growers with insufficient alternatives to manage the CSFB threat. Consequently, UK OSR growing area is at a 41-year low (AHDB, 2025).

Genetic-based resistance offers a component of an integrated pest management approach that can be utilised for crop protection, however limited resistance exists within our current commercial gene pool. Expanding our search into Brassica wild relatives which have retained a higher level of resistance to CSFBs may provide us with novel genetics to utilise in breeding for insect resistance. Sinapis alba, white mustard, has long been recognised as having higher resistance to several insect pests, including tarnished plant bugs, Lygus lineolaris (Bodnaryk, 1995) and other flea beetles, Chrysomelidae species (Brandt & Lamb, 1993). However, little is known about the resistance of S. alba to CSFBs, nor the underlying genetics.

Within this project we have utilised 148 readily available S. alba accessions with the aim of identifying novel genetic and phenotypic characteristics associated with palatability to adult CSFB. Accessions were scored for key phenotypic traits including seed morphology, flowering time, and trichome densities. Analysis with fluoro-labelled single sequence repeat (SSR) markers was used to identify population structure and combined with the phenotypic and accession origin data to determine a subset of 65 lines for CSFB herbivory screening using non-choice assays. Analysis identified significant variation for adult feeding and genotypes showing extreme levels of feeding were determined. Direct comparisons of those contrasting phenotypes have revealed further insights into the physical, chemical and genetic bases for CSFB resistance in S. alba.

Finally, novel S. alba material was investigated for its potential for crossing into commercial Brassica germplasms and a direct hybridisation between S. alba and B. rapa was possible through the use of additional rescuing techniques.

This thesis provides insights into the extent of natural variation across S. alba, how this translates into CSFB resistance, and which traits may influence the level of resistance seen. Promising accessions possessing novel genetics and traits linked to higher CSFB resistance, will provide opportunities for recruitment into future OSR breeding programmes for improving pest resistance.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	01 Jun 2026 13:00
Last Modified:	01 Jun 2026 13:00
URI:	https://ueaeprints.uea.ac.uk/id/eprint/103220
DOI:

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