Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Positional Cloning Of Powdery Mildew And Yellow Dwarf Virus Resistance Genes In Barley

Nicholas C Collins^1,2 , Paul Schulze-Lefert³ , Hans Thordal-Christensen⁴ , Robert H Symons⁵ , Peter Langridge¹

¹  Australian Centre for Plant Functional Genomics, Glen Osmond, SA, 5064, Australia

²  Formerly Sainsbury Laboratory, John Innes Centre, Norwich, Norfolk, NR4 7UH, UK

³  Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg, Köln, 50829, Germany

⁴  Plant Research Department, Risř National Laboratory, Roskilde, DK-4000, Denmark

⁵  Formerly Department of Plant Science, University of Adelaide, Glen Osmond, SA, 5064, Australia

Work on several disease resistance genes from barley will be described. The Ror1 and Ror2 genes defined via mutants are components of cell wall penetration resistance against both compatible races (partial resistance) and incompatible wheat races (non-host resistance) of powdery mildew fungi. Co-linearity with rice facilitated the rapid cloning of Ror2, encoding a plasma membrane syntaxin, and the identification of a functional homologue in Arabidopsis (Pen1). A single plant cell gene expression/silencing system, and sub-cellular localization and protein interaction assays were employed to investigate Ror2/Pen1 function, revealing a novel conserved resistance mechanism at the cell periphery involving a specific, and likely exocytosis-mediating, SNARE complex containing the Ror2/Pen1 syntaxin.
The Yd2 gene confers durable resistance against Barley Yellow Dwarf Virus (BYDV), a serious pathogen of cereals worldwide. Isolation of Yd2 is being pursued using conventional genetic mapping approach, as well as using linkage disequilibrium mapping with Ethiopian landrace barleys which are the original source of Yd2 resistance alleles.
General approaches for targeted PCR marker generation using the rice sequence will be reported. In the vicinity of Ror1 and Yd2 located close to the centromeres of chromosomes 1H and 3H respectively, recombination in the mapping populations was found to be highly localized. Based on limited available linkage disequilibrium data, recombination in these regions may be similarly restricted in the wider barley germplasm.