Characterisation of a genetic region that conditions resistance to viral fungal and plasmodiophorid plant pathogens

Plant resistance (R) genes form an important component of integrated pest management strategies, decreasing reliance on fungicide and insecticide treatments. Recent work within our consortium has resulted in the identification of an R gene region that conditions resistance to viral, fungal and plasmodiophorid pathogens of sugar beet. This broad-spectrum resistance could be conferred by a number of tightly-linked R genes or by a single, novel gene. Subsequent scans of the genome revealed a number of loci that interacted with the broad-spectrum R gene locus to reduce disease levels. The aim of the project is to characterise the region of Beta vulgaris chromosome IV involved in resistance to diverse pathogens, in terms of its structure, its interaction with secondary genetic loci and its ability to control disease in the field. It is anticipated that the information and materials generated within the project will be used for marker assisted selection by sugar beet breeders and potentially for map-based cloning of the resistance gene(s) in subsequent work. A further aim of the project therefore is to facilitate further exploitation of this resistance locus. In year 1, large plant populations which segregate for resistance to diverse pathogens will be evaluated for disease resistance in controlled environment tests. Industry partners will conduct molecular marker analysis on these populations so that QTL maps can be generated. These maps will be used to identify secondary, interacting loci and to define a region of chromosome IV that contains the resistance alleles. Individual plants that show recombination in this region will be used to generate testcross families for fine mapping. In year 2, a set of polymorphic SNP markers will be generated and mapped within the region of interest. In year 3, the testcross families will be evaluated for disease resistance over a growing season in the field, allowing the efficacy of chromosome IV resistance through time to be determined. This phenotypic information will be combined with the SNP marker data to generate Mendelised, fine maps of the broad-spectrum resistance locus. The results and interpretation of this work will be submitted to peer review journals.