Cereal crops are highly vulnerable to heat stress. Pollen development is particularly susceptible to high temperatures. Heat stress has been shown to result in pollen inviability and male sterility. Wheat exposed for 3 days at 30°C during pollen development was found to have a 35% reduction in grain set. With global temperatures set to rise by a further 0.82.6°C by 2050, heat induced loss of yield is set to increase. The phytohormones, gibberellins (GAs), auxins, jasmonates (JAs) and ethylene have an important role in controlling pollen development and are also implicated in regulating heat stress responses. This project aims to improve our understanding of the role of phytohormones in heat stress, with a view to developing chemical or genetic strategies to reduce the associated yield losses. The reverse genetics-based approach of TILLING has been used to identify potential mutants affecting auxin, JA, ethylene and gibberellin signalling. This involved identifying gain-of-function mutants in the wheat Aux/IAA, JAZ and ethylene receptor protein families; and loss-offunction mutants in the three homoeologues of wheat GA-MYB. The mutant lines have been backcrossed twice to remove 75% of non-related EMS mutations. We aim to investigate the impact these mutations have on anther/pollen development and heat stress tolerance. This will be complemented by performing global hormone and qRT-PCR analysis on anthers to establish the importance of these pathways during heat stress responses. These studies are expected to provide new insights into phytohormone regulation of anther development and the heat stress response in wheat.