Canola, Rapeseed, and Mustard: For Biofuels and Bioproducts - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 138

Genetic Resources
The genetic diversity in the Brassicaceae family is very large. Crosses between a
large number of wild and cultivated Brassica species are possible despite large
differences in chromosome numbers. A comprehensive listing of the numerous
crosses possible within the Brassicaceae has been reported by [ 51 ]. Interspecific
crosses in the Brassicaceae are most frequently made among species in the U
triangle (Fig. 7.1 ). Crosses between each amphidiploid species and their two
respective diploid parents as well as between amphidiploids having a parental
genome in common are readily possible [ 41 ]. In addition, intergeneric crosses
between Diplotaxis , Eruca , Raphanus , and Sinapis genera to one or more of the
diploid Brassica species in the U triangle are possible [ 41 ]. As a general rule, the
interspecific crosses are more successful if the amphidiploid parent in the cross is
used as the female parent [ 46 ]. Crosses between the diploid species of the U triangle
are possible, but these have a low success rate [ 52 ]. Crosses of the diploid species
which originally created the amphidiploid species have been successfully repeated
by researchers to create resynthesized hybrids for B. carinata , B. napus , and
B. juncea [ 41 ]. These resynthesized hybrids display poor agronomic performance,
poor seed quality, moderate to high erucic acid content, and high glucosinolate
content, rendering them of little direct use; however, they have been used as
bridging species for transferring desirable genes or traits from the diploid parent
species into adapted amphidiploid cultivars [ 53 ]. Resynthesis of the amphidiploid
species to enhance the genetic variability of B. napus , B. carinata , and B. juncea
also has been and continues to be a frequently used approach in amphidiploid
species breeding [ 43 , 46 ].
While a huge number of interspecific crosses within Brassica can be success-
fully undertaken, few are actually attempted. Some Brassica researchers have
indicated that the available natural variation in Brassica oilseeds has not yet been
fully assessed or exploited with few exceptions and suggest that systematic searches
will identify the needed traits within the six Brassica species in the U triangle
[ 46 ]. Regardless of the reasons, most canola/rapeseed/mustard breeding programs
tend to stay within an even more restricted gene pool of adapted Brassica material
as genetic resources [ 54 , 55 ].
There are large public gene bank collections of Brassica species cultivars/lines
located in the United Kingdom, Germany, the United States, India, and China [ 16 ,
56 ]. Bioversity International, formerly International Plant Genetic Resources Insti-
tute (IPGRI), a member of the Consultative Group on International Agricultural
Research (CGIAR) consortium, collects and preserves Brassica species accessions
and maintains a Germplasm Database website ( ecpgr.cgiar.org/germplasm_data
bases.html ) [ 57 ] that provides information on accessions of Brassica species
cultivars/lines stored in gene bank collections globally. There are Brassicaceae
collections held at the Universidad Polit´cnica de Madrid, Spain [ 58 ]; the Tohoku
University, Japan; the Nordic Gene Bank in Sweden; and the Australian Temperate
Field Crops Collection in Australia [ 16 ].