High yield potential, shuttle breeding, genetic diversity, and a new international wheat improvement strategy Rodomiro Ortiz Æ Richard Trethowan Æ Guillermo Ortiz Ferrara Æ Masa Iwanaga Æ John H. Dodds Æ Jonathan H. Crouch Æ Jose Crossa Æ Hans-Joachim Braun Received: 12 September 2006 / Accepted: 28 January 2007 / Published online: 16 February 2007 Ó Springer Science+Business Media B.V. 2007 Abstract The main elements of the international wheat improvement program of the Centro Internacional de Mejoramiento de Maı´z y Trigo (CIMMYT), also known as the International Maize and Wheat Improvement Center, have been shuttle breeding at two contrasting locations in Mexico, wide adaptation, durable rust and Septoria resistances, international multisite test- ing, and the appropriate use of genetic variation to enhance yield gains of subsequently produced lines. Such an approach yielded successes known collectively as the Green Revolution. However, at the beginning of the 21st century, this ‘‘cultivar assembly line’’ approach needs fine tuning to address crop needs under increasingly adopted resource conserving practices, as well as those related to nutritional requirements of the end- users. International wheat improvement will therefore focus on the targeting of traits in respective mega-environments, and the use of participatory methods, especially in marginal environments. The main features of this wheat improvement strategy include the introduction of new and novel sources of genetic variation through wild species, landraces, and, potentially, the use of transgenes for intractable traits. This variation will be combined using international shuttle breeding, and increased breeding effi- ciency will be achieved through marker-aided methods, more targeted use of crop physiology, plant genetics, biostatistics, and bioinformatics. Likewise, CIMMYT will increase its focus on the needs of end-users by emphasizing regional efforts in participatory research and client-ori- ented plant breeding. Keywords Genetic diversity Á Genotype-by- environment interaction Á Green Revolution Á International breeding Á Marker aided breeding Á Multilocation testing Á Selection methods Introduction The 1970 Nobel Peace Prize Laureate, Dr. Norman Ernst Borlaug, shaped international wheat improvement philosophy. His legacy includes shuttle breeding, wide adaptation, dura- ble disease resistance, international multisite testing, and the wise use of genetic variability. While shuttle breeding, wide adaptation, durable R. Ortiz (&) Á R. Trethowan Á M. Iwanaga Á J. H. Dodds Á J. H. Crouch Á J. Crossa Centro Internacional de Mejoramiento de Maı ´z y Trigo (CIMMYT), Apdo. Postal 6-641, 06600 Mexico, DF, Mexico e-mail: r.ortiz@cgiar.org G. O. Ferrara CIMMYT, Katmandu, Nepal H.-J. Braun CIMMYT, Ankara, Turkey 123 Euphytica (2007) 157:365–384 DOI 10.1007/s10681-007-9375-9