The success of plant breeding over the past cen-
tury has been associated with a narrowing of
the available genetic diversity within elite germ-
plasm, particularly for some species such as
peanut and soybean. New sources of variation
include landraces and wild relatives of crop
species, and although exploiting wild relatives
as a source of novel alleles is challenging, it has
provided notable successes in crop improve-
ment. A particularly important example of the
introgression of genetic information from a rela-
tive was the use of the short arm of rye chro-
mosome 1R in wheat. In the early 1990s, this
wheat-rye translocation was used in 45% of 505
bread wheat cultivars in 17 countries (21). In-
creasingly easy gene discovery, improved en-
abling technologies for genetics and breeding,
and a better understanding of the factors lim-
iting practical exploitation of exotic germplasm
promise to transform existing, and to accelerate
the development of new, strategies for efficient
and directed germplasm use (Box 1).
Most crop geneticists agree that enrichment
of the cultivated gene pool will be necessary to
meet the challenges that lie ahead. However,
to fully capitalize on the extensive reservoir of
favorable alleles within wild germplasm, many
advances are still needed. These include increas-
ing our understanding of the molecular basis for
key traits, expanding the phenotyping and geno-
typing of germplasm collections, improving our
molecular understanding of recombination in
order to enhance rates of introgression of alien
chromosome regions, and developing new breed-
ing strategies that permit introgression of multi-
ple traits (22). Recent progress has shown that
each of these challenges is tractable and within
reach if some of the basic problems limiting the
application of new technologies can be tackled.