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Humankind will face unprecedented challenges in the twenty-fi rst century, includ-
ing growing pressure on agricultural production, in particular, major staple crops
such as wheat. In order to cope with a suite of climatic, environmental and socio-
economic changes and achieve food security in a sustainable manner, it will be criti-
cal to grow varieties of wheat with increased resistance to diseases, pests and
adverse environmental conditions and with improved yield, as well as to reduce
post-harvest losses and employ improved agronomic practices. However, the devel-
opment of suitable varieties may be limited by the narrow genetic diversity of wheat
germplasm, which is the result of selection pressure imposed during wheat domes-
tication and many years of breeding. An approach that could play an important role
in breeding novel wheat cultivars relies on the use of alien germplasm, including
relatively distant gene pools, which represent an attractive source of value-added
traits. The need to counteract wheat genetic erosion was highlighted by the intensive
selection pressures encountered in the twentieth century’s Green Revolution.
The idea of interspecifi c hybridization attracted researchers and breeders long
ago, and the fi rst successful crosses were already reported in the eighteenth century.
The production of a wheat–rye hybrid in 1876 by the Scottish botanist A. Stephen
Wilson was a milestone in the efforts to hybridize wheat with related species.
Although the hybrid was sterile, intensive programs were set up in many countries
with the hope of incorporating useful traits of rye into wheat and soon led to the
development of fertile wheat–rye hybrids. A notable case of the early efforts to
transfer alien genes from related species into wheat was carried out by Edgar
S. McFadden, a USDA agronomist at the Texas Agricultural Experiment Station,
and Ernest R. Sears, a USDA geneticist at the University of Missouri, Columbia.
During a long-lasting, fruitful collaboration initiated in 1938, McFadden’s determi-
nation to use wide crosses in wheat breeding could be realized thanks to the meth-
ods and cytogenetic tools developed by Sears. Unfortunately, the initial efforts in
“radical breeding” were ineffi cient due to hybrid sterility and linkages between
desirable and undesirable trait loci. Nonetheless, their work not only contributed to
the breeding, cytology, genetics, phylogeny, taxonomy and evolution of wheat but