Exploiting Genetic Resources to Identify Genetic Resistance to Septoria Tritici Blotch

Septoria tritici blotch (STB) is the most devastating fungal disease of wheat in Ireland. Here, we will employ a multifaceted approach to explore host-response to STB.

The first approach is bulked-segregant analysis (BSA) by RNA-seq of a Triticum aestivum doubled-haploid, and a recombinant inbred Brachypodium distachyon population. Phenotype screens of these populations reveal that they are both under transgressive segregation for STB resistance, suggesting quantitative inheritance of STB resistance and susceptibility genes.

We are sequencing the transcriptome of the phenotypic extremes of both populations, in a time-course, to target genes with differential expression (DEGs) between the resistant and susceptible hosts during early infection.

The second approach is a modification on the recently developed associative transcriptomics method. Forty elite wheat varieties have been screened for resistance to STB, and final panels of resistant and susceptible varieties have been chosen for RNA-seq as bulks. This approach will target DEGs between these resistant and susceptible bulks, and will also allow us to identify resistance and susceptibility genes that are common between the varieties.

Finally, we have screened ~1500 lines of the Cadenza TILLING population for STB resistance. Several lines are showing resistance and altered susceptibility to STB, compared to T. aestivum cv. Cadenza. Backcrossing of these candidate lines to Cadenza is underway, and exome-capture of BC₅ lines will be used to identify allelic differences between the resistant lines and cv. Cadenza.

Interesting genes will be chosen for characterisation, and SNP markers will be developed for use in breeding programmes.