Canola, Rapeseed, and Mustard: For Biofuels and Bioproducts - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 146

[ 134 ]. QTL identification for numerous traits in Brassica oilseeds is common, for
example, QTL for oil content in B. napus [ 135 ].
Marker-assisted selection is being successfully used in Brassica oilseed breeding
programs. For example, the development of genome-specific erucic acid gene
molecular markers for the two erucic acid controlling genes in B. napus [ 136 ] has
permitted the selection of homozygous canola and high erucic acid genotypes in
segregating generations and backcross generation progeny of canola x HEAR
crosses, greatly improving breeding efficiency for such programs.
Brassica oilseeds are highly amenable to all of the procedures required to
transform plants. The disarmed Agrobacterium tumefaciens vector has been used
routinely to move cloned genes into the chromosomes of Brassica oilseed species
[ 137 ]. Many of the herbicide tolerance systems and the NMS pollination control
system have been developed using B. napus transformation technology.
More recently, very-high-throughput sequencing is providing genome sequenc-
ing, genome resequencing, and targeted resequencing capabilities for all plant
genomes including Brassica oilseeds. This technology will facilitate the complete
assessment of individual Brassica genotypes by sequencing, an advanced form of
genomics-based assisted selection.
Seed Production
Flower type, pollination type, and crop type have considerable impact on seed
production procedures used in different crops. The vast majority of the Brassica
species are perfect flowered types [ 18 ]. Further, as a general rule, for the six
Brassica species of the U triangle, the diploid species ( B. nigra , B. oleracea , and
B. rapa ) are self-incompatible obligate outcrossing species, while the amphidiploid
species ( B. carinata , B. juncea , and B. napus ) are self-compatible self-pollinating
species [ 54 ]. However, variations exist among plant types for pollination mode
within species [ 138 ]. For example, B. rapa var. sarson (brown and yellow) and
B. oleracea var. alboglabra are exceptions, since they are self-compatible diploids.
Pollen transfer between plants can occur by physical contact or by insects for the
self-compatible species and by physical contact, by wind, or by insects for the self-
incompatible species.
There are numerous crop types in the Brassica oilseed species. Cultivars for the
diploid species are usually genetically diverse outcross populations, while cultivars
for the amphidiploid species can be pure inbred or DH lines, open-pollinated
populations, synthetics, or hybrids. B. napus canola/rapeseed hybrid cultivars are
rapidly becoming the predominant type in this species grown throughout the world.
Brassica species seed multiplication rates are very high, from 300 to 1,000:
1[ 41 ], so a limited number of generations of seed multiplication are needed to
produce the required quantities of commercial planting seed [ 139 ] for all cultivar
types. The canola/rapeseed/mustard pedigreed seed generational cascade in Canada
involves breeder seed, foundation seed, and certified seed [ 140 ].