Validation of genome wide association studies (GWAS) for the identification of candidate genes associated with virulence in Parastagonospora nodorum
Y. GAO (1), Z. Liu (1), J. Faris (2), J. Richards (1), R. Brueggeman (1), R. Oliver (3), B. McDonald (4), T. Friesen (2) (1) Plant Pathology Department, North Dakota State University, U.S.A.; (2) NCSL, USDA-ARS, U.S.A.; (3) School of Science, Curtin University, Australia; (4) Institute of Integrative Biology, Plant Pathology Group, Swiss Federal Institute of Technology, Switzerland

Parastagonospora nodorum is a necrotrophic fungal pathogen causing Septoria nodorum blotch (SNB) on wheat. In P. nodorum, three necrotrophic effectors (NEs), SnToxA, SnTox1 and SnTox3 which are critical to virulence have been characterized. To identify additional NE gene regions, we conducted a genome wide association study (GWAS) using a natural population of 191 P. nodorum isolates with 2,986 single nucleotide polymorphisms (SNPs). SnToxA and SnTox3 gene markers were used to evaluate the power of GWAS on wheat lines Sumai3 and Alsen. Strong marker trait associations (MTAs) with pathogen virulence were identified at SnTox3 and SnToxA loci, indicating GWAS is an effective way to identify fungal virulence. In addition, a novel locus conferring virulence toward Sumai3 and Alsen was identified. To increase marker saturation, a set of presence/absence markers were added in the SnToxA and SnTox3 genomic regions. The marker proximity necessary to identify MTA flanking SnToxA and SnTox3 ranged from 4-5 kb and 2-7 kb, respectively, showing that the rate of linkage disequilibrium decay in P. nodorum is high and can be an advantage if sufficient marker density is attained. After adding more markers in the novel region, a 4.6 kb genomic region was defined by four highly significant SNPs. Within that region, genes encoding one small secreted protein and three proteins less than 50 kDa were predicted. Gene knockouts and transformation are being done to validate these candidate genes.

Abstract Number: P11-356
Session Type: Poster