Exploring root resistance to take-all disease from wheat landraces and ancestral wheat relatives

Wheat is regarded as one of the three most important crops for human calorie intake and livestock feed. This project aims to further characterise and genetically define resistance to take-all disease found in an ancestral wheat relative, T. monococcum. Characterising the mechanism of resistance will enhance our knowledge of such interactions and potentially lead to new methods of disease control and improved root health that could be used in farming practices of wheat worldwide. Identifying the locus/ loci conferring this resistance will have future applications through introducing such genes into commercially grown wheat varieties. Take-all disease has been linked to yield losses of up to 60% in wheat and yet control methods are very limited, with currently no identified genes for resistance. Therefore, outcomes of this research could improve wheat performance from new cultivars with genetic resistance to root disease, reducing the reliance on crop rotation or chemical interventions.

This take-all disease resistance/wheat root health study will involve the following possible experiments:
1.The genetic basis of resistance will be investigated using the diploid wheat Triticum monococcum (Tm) mapping population derived from a cross MDR031 (resistant) x MDR043 (susceptible). Third wheat field trials have already been carried out in 2017 and 2018, and this will be replicated in 2019. Sampled and stored root systems will be visually scored for resistance to take-all.
2. A molecular marker map will be generated for the MDR031 x MDR043 population based on a combination of known SSR markers and newly developed KASP markers using SNP information from restriction-site associated DNA (RAD) sequencing as well as the data from the defra funded wheat promotome capture experiment within WGIN3. Molecular markers closely flanking the resistance QTL or QTLs will be determined.
3. The resistance present in MDR031 is currently being introgressed into the hexaploid wheat cv. Paragon as part of the defra funded WGIN4 project. Once the backcross generation has reached stage 4, the associated molecular markers identified (in 2 above) will be used on plants to determine which harbour the QTL of interest.
4. A collection of take-all isolates will be recovered from the parental Tm lines as well as hexaploid wheat Hereward from field samples and characterised for type, sensitivity to the chemistry silthiofam and via ITS sequencing. The properties of this new collection will be compared with those of the main RRes collection.
5. The influence of take-all on the yield of MDR031 and MDR043 will be explored by devising a new ear sampling protocol when Tm is grown in 1st and 3rd wheat situations. Tolerance of Tm to take-all disease has not previously been explored.
6. A potentially susceptible rye species will initially be re-investigated in pot tests. If proven to be susceptible, this rye accession will be crossed to a resistant rye and the genetic basis of resistance explored in subsequent generations. The two ryes will also be grown and evaluated in 1st and 3rd wheat field trials to determine adult plant performance and to recover take-all isolates able to colonise rye roots. The mechanisms underlying susceptibility and resistance of rye to take-all will also be studied in pot tests and other types of assays.
7. Near isogenic lines (NILs) in the cv. Chinese Spring harbouring the 3N QTL introgressed from Aegilops uniaristata, conferring prolific root development will be studied for their response to take-all infection in pot and 1st and 3rd field experiments and the altered root architecture quantified.
8. A comparative microbiome analysis will be done using the Tm parental lines and Hereward in field trials to explore whether the species profile in the rhizosphere and endosphere is altered in the presence of the resistance conferred by MDR031.