Turnip mosaic virus determinants of virulence for Brassica napus resistance genes

Abstract

Dominant resistance genes identified in Brassica napus lines are effective against some, but not all, Turnip mosaic virus(TuMV) isolates. An infectious clone of an isolate (UK 1) was used as the basis of chimeric virus constructions usingresistance-breaking mutants and other isolates to identify the virulence determinants for three dominant resistance genes.For the resistance gene TuRB01, the presence of either of two mutations affecting the cylindrical inclusion (CI) proteinconverted the avirulent UK 1 to a virulent isolate. Acquisition of such mutations had a slight cost to viral fitness inplants lacking the resistance gene. A similar strategy is being used to identify the virulence determinants for two moreresistance genes present in another B. napus line.

Keywords

• turnip mosaic virus
• brassica napus
• resistance genes
• pathogenicity determinants