Identifying variation in resistance to the take-all fungus, Gaeumannomyces graminis var. tritici, between different ancestral and modern wheat species

Background: Ancestral wheat relatives are important sources of genetic diversity for the introduction of novel traits
for the improvement of modern bread wheat. In this study the aim was to assess the susceptibility of 34 accessions
of the diploid wheat Triticum monococcum (A genome) to Gaeumannomyces graminis var. tritici (Ggt), the causal
agent of take-all disease. The second aim was to explore the susceptibility of tetraploid wheat (T. durum) and the B
genome progenitor species Aegilops speltoides to Ggt.

Results: Field trials, conducted over 5 years, identified seven T. monococcum accessions with a good level of
resistance to take-all when exposed to natural inoculum under UK field conditions. All other accessions were highly
susceptible or did not exhibit a consistent phenotype across years. DArT marker genotyping revealed that whole
genome diversity was not closely related to resistance to take-all within T. monococcum, suggesting that multiple
genetic sources of resistance may exist within the species. In contrast the tetraploid wheat cultivars and Ae. speltoides
were all highly susceptible to the disease, including those with known elevated levels of benzoxazinoids.

Conclusions: The diploid wheat species T. monococcum may provide a genetic source of resistance to take-all disease
that could be utilised to improve the performance of T. aestivum in high disease risk situations. This represents an
extremely valuable resource to achieve economic and sustainable genetic control of this root disease.