Genome Analysis and Avirulence Gene Cloning Using a High-Density RADseq Marker Linkage Map for the Flax Rust Fungus, Melampsora lini.
P. DODDS (1), C. Anderson (2), A. Catanzariti (2), N. Upadhyaya (1), J. Chen (3), R. Mago (1), A. Nemri (1), W. Wu (2), S. Williams (4), S. Periyannan (1), B. Xu (1), M. Bernoux (1), R. Park (3), J. Ellis (1), B. Kobe (4), A. Hardham (2), D. Jones (2) (1) CSIRO Agriculture Flagship, Canberra, Australia; (2) Research School of Biological Sciences, Australian National University, Canberra, Australia; (3) Plant Breeding Institute, University of Sydney, Narellan, Australia; (4) School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia

Rust fungi such as Melampsora lini (flax rust) and Puccinia graminis fsp tritici (Pgt, wheat stem rust) form specialised haustoria structures during infection that serve as nutrient uptake sites as well as delivering effector proteins to the host cell. M. lini has served as a model rust to investigate the molecular basis of the recognition events between R and Avr proteins, and we are now extending this work into the Pgt system. Four avirulence (Avr) loci are known in flax rust and encode effectors that are recognised by host nucleotide-binding and leucine-rich repeat (NB-LRR) resistance proteins. Recently we generated a draft genome sequence of 190Mbp for flax rust represented in 21,000 contig sequences. Using RADseq, we have scored ~13,000 SNP markers in an M. lini F2 family to generate a large scale linkage map that has allowed anchoring of 67% of the genome sequence onto 27 linkage groups. This process identified physical regions co-segregating with several Avr genes and one avirulence inhibitor locus. Two new Avr genes have been cloned and confirmed by expression in resistance flax lines. Gene expression profiling during rust infection of flax reveals a common expression pattern for a subset of effector candidates that includes all of the known Avr genes. We have also generated genome sequence and effector candidate predictions in Pgt and are using a mutational approach to identify Avr genes. Several Pgt mutants have been isolated that have gained virulence on Sr50, Sr5 and Sr27 and genome sequence analysis has identified a range of large deletion events in these lines identifying the corresponding genomic regions and associated genes. Understanding the nature of wheat R genes and the Avr proteins that they recognize will allow better prediction of R gene durability and choice of the optimal combinations of R genes to deploy in gene stacks.

Abstract Number: C2-3
Session Type: Concurrent Session