Acknowledgments Financial support provided by the Australian Centre for International Agricultural Research (ACIAR) is acknowledged by participants of the International Symposium Challenges to International Wheat Improvement, CIMMYT, Obregon, Mexico, 20–24 March 2006, including the authors listed below publishing in this special issue of Euphytica. CI-MMYT and CSIRO would also like to acknowledge ACIAR’s contribution to the project ‘Increasing yield potential in wheat: complementing conventional breeding by application of novel physiological and germplasm strategies’ (LWR2/1998/014) between 1999 and 2007 that led up to the current forum of international wheat researchers.