Effects of temperature on wheat-pathogen interactions

Climate change is affecting UK agriculture, and research is needed to prepare crops for the future. Wheat is the UK’s most important crop, and needs to be protected from losses caused by disease. While direct effect of the environment on pathogen spread is often reported, effect of the environment on host defence is not. Many wheat resistance genes are temperature sensitive and these were used as a starting point to investigate defence temperature sensitivity in wheat starting with yellow rust resistance gene Yr36, previously shown to be temperature-sensitive. The effect of temperature on resistance was shown to be independent of Yr36 in breeding line UC1041, and was more likely to be due to a previously-uncharacterised background temperature sensitivity. These results suggest that temperature changes, rather than thresholds, might influence some disease resistance mechanisms. Understanding this phenomenon could enable the breeding of more stable defence in crops. In order to gain further insight into how temperature changes influence resistance, plants were grown under different thermoperiods and challenged with different types of pathogens; Results showed that resistance to multiple pathogens in one cultivar Claire was enhanced under variable temperatures, compared to constant temperatures. Taken together, the research presented revealed that defence temperature sensitivity in plants is much more complex than previously thought, considering that both temperature changes and different thermoperiods can influence aspects of wheat defence. To ascertain which research approaches will be most valuable in preparing for climate change, the effect of the environment on take-all was also investigated. Vulnerable periods for wheat from the threat of take-all development were identified by analysing historical datasets, and controlled environment experiments. Results showed a relationship between initial post-sowing temperatures and spring take-all levels in 2nd 3rd or 4th winter wheats, depending on the location. The work on yellow rust resistance and take-all both identify vulnerable periods for wheat caused by the environment, be it weakening of host defence responses, or increased threat from disease pressure. Further characterisation and understanding of vulnerable periods will be essential to control disease outbreaks under an increasingly unstable climate