Resistance gene cloning in wheat by mutational genomics
B. WULFF (1), B. Steuernagel (1), S. Periyannan (2), I. Hernandez-Pinzon (3), K. Witek (4), M. Rouse (5), G. Yu (1), A. Hatta (1), M. Ayliffe (2), H. Bariana (6), J. Jones (4), E. Lagudah (2) (1) John Innes Centre, United Kingdom; (2) CSIRO, Australia; (3) The Sainsbury Laboratory, Australia; (4) The Sainsbury Laboratory, United Kingdom; (5) USDA, U.S.A.; (6) University of Sydney, Australia

Plant disease resistance (R) genes often reside in complex clusters that display extreme accessional copy number and sequence diversity. This obscures orthogonal relationships and leads to uneven or suppressed recombination, thus complicating the identification of R genes by map-based approximation. In polyploid bread wheat this is further confounded by the large genome (~17 Gb), high content of repetitive transposon DNA (80%), large chromosomal duplications, and the presence of three homeoelogous chromosomes. To overcome these challenges we have developed an approach to R gene cloning based on (i) mutagenesis and screening to obtain multiple, independently derived loss-of-function mutants, (ii) resistance gene enrichment sequencing (exome capture for NB-LRRs), and (iii) sequence comparison between mutants and wild-type. Our method, dubbed MutRenSeq, does not rely on recombination for fine mapping, nor does it require the construction of a physical BAC contig across a mapping interval. We have demonstrated the efficacy of our method in hexaploid wheat by cloning the wheat stem rust R genes Sr22 and Sr45. Our longterm aim is to develop a transgene stack containing multiple broad-spectrum Sr genes for more durable stem rust resistance.

Abstract Number: S6-5
Session Type: Special Session