Functional Genomics for Novel Fungal Pathogen Resistance in Wheat

In model plants, resistance to a range of pathogens has been achieved via modification of host genes. We are harnessing information obtained from research in model plants, in conjunction with rapidly increasing functional genomics capabilities, to achieve novel resistance to fungal pathogens in wheat (with an emphasis on Fusarium pseudograminearum, the causal agent of crown rot). Initially, wheat lines lacking homologues of six candidate 'susceptibility genes' were identified within a mutant population (reverse genetics). Furthermore, to overcome functional redundancy in hexaploid wheat, a crossing strategy was undertaken to combine deletions of homoeologous copies of these genes. Mutation discovery using next-generation sequencing technology is now being used to identify mutations in 90 additional wheat genes with putative roles in fungal pathogen resistance. Additionally, large-scale phenotypic screening of mutagenized wheat populations (forward genetics) is being undertaken to identify mutants with increased resistance to the necrotroph Fusarium pseudograminearum and, by contrast, the biotroph Puccinia striiformis. Genomic techniques will be explored to identify causal mutations for genetically tractable resistance identified in these lines. Finally, we have discovered that the cereal model Brachypodium distachyon is highly susceptible to Fusarium crown rot. By exploiting burgeoning Brachypodium genomic resources we aim to identify Brachypodium genes with key roles in crown rot resistance or susceptibility, homologues of which would become strong candidates for inactivation or over-expression in hexaploid wheat. The complementary functional genomic approaches being explored should assist with the development and maintenance of wheat germplasm that is highly resistant to crown rot and other fungal pathogens.