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Bipolaris sorokiniana is the causal agent of multiple diseases on wheat and barley and is the primary constraint to cereal production throughout South Asia. Despite its significance, the molecular basis of disease is poorly understood. To address this, the genomes of three Australian isolates of B. sorokiniana were sequenced and screened for known pathogenicity genes. Sequence analysis revealed that the isolate BRIP10943 harboured the ToxA gene, which has been associated previously with disease in the wheat pathogens Parastagonospora nodorum and Pyrenophora tritici-repentis. Analysis of the regions flanking ToxA within B. sorokiniana revealed that it was embedded within a 12-kb genomic element nearly identical to the corresponding regions in P. nodorum and P. tritici-repentis. A screen of 35 Australian B. sorokiniana isolates confirmed that ToxA was present in 12 isolates. Sequencing of the ToxA genes within these isolates revealed two haplotypes, which differed by a single non-synonymous nucleotide substitution. Pathogenicity assays showed that a B. sorokiniana isolate harbouring ToxA was more virulent on wheat lines that contained the sensitivity gene when compared with a non-ToxA isolate. This work demonstrates that proteins that confer host-specific virulence can be horizontally acquired across multiple species. This acquisition can dramatically increase the virulence of pathogenic strains on susceptible cultivars, which, in an agricultural setting, can have devastating economic and social impacts., (© 2017 BSPP AND JOHN WILEY & SONS LTD.)

The wheat pathogen Stagonospora nodorum, causal organism of the wheat disease Stagonospora nodorum blotch, has emerged as a model for the Dothideomycetes, a large fungal taxon that includes many important plant pathogens. The initial annotation of the genome assembly included 16,586 nuclear gene models. These gene models were used to design a microarray that has been interrogated with labelled transcripts from six cDNA samples: four from infected wheat plants at time points spanning early infection to sporulation, and two time points taken from growth in artificial media. Positive signals of expression were obtained for 12,281 genes. This represents strong corroborative evidence of the validity of these gene models. Significantly differential expression between the various time points was observed. When infected samples were compared with axenic cultures, 2882 genes were expressed at a higher level in planta and 3630 were expressed more highly in vitro. Similar numbers were differentially expressed between different developmental stages. The earliest time points in planta were particularly enriched in differentially expressed genes. A disproportionate number of the early expressed gene products were predicted to be secreted, but otherwise had no obvious sequence homology to functionally characterized genes. These genes are candidate necrotrophic effectors. We have focused attention on genes for carbohydrate metabolism and the specific biosynthetic pathways active during growth in planta. The analysis points to a very dynamic adjustment of metabolism during infection. Functional analysis of a gene in the coenzyme A biosynthetic pathway showed that the enzyme was dispensable for growth, indicating that a precursor is supplied by the plant., (© 2011 The Authors. Molecular Plant Pathology © 2011 BSPP and Blackwell Publishing Ltd.)