Canola, Rapeseed, and Mustard: For Biofuels and Bioproducts - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 143

the seed oil has been reported by [ 62 ]. This indicates that SHEAR development
from HEAR is possible using transgenic technologies.
The breeding strategy to develop canola-quality B. juncea (canola-quality mus-
tard) has involved identification of natural mutant zero erucic acid mustard lines
[ 59 ] and interspecific cross-derived low glucosinolate mustard lines [ 76 ]. Crosses
of the low erucic acid lines with the low glucosinolate lines were used to develop
canola B. juncea [ 11 ].
Disease resistance especially to blackleg was greatly improved in Canadian
canola/rapeseed cultivars using European and Australian sources of blackleg resis-
tance within B. napus initially, but later using B. juncea as a blackleg resistance
gene source [ 77 ] and wild B. rapa subsp. sylvestris as a blackleg resistance gene
source [ 78 ].
Several different breeding strategies have been used to develop herbicide-
tolerant canola/rapeseed/mustard in Canada. Triazine tolerance, the first herbicide
tolerance to be developed in Canada, was transferred from naturally occurring
mutant B. rapa plants to B. napus using a backcross approach to insert the
B. napus nucleus into the B. rapa cytoplasm [ 79 ].
Glufosinate-tolerant B. napus was created using transformation technology to
add a gene for an enzyme from a soil actinomycete which detoxified glufosinate to
B. napus canola [ 80 ]. Glufosinate tolerance is also part of the genetically
engineered nuclear male sterility (NMS) system created by Bayer CropScience
[ 81 ], which is used to produce InVigor hybrid canola cultivars [ 43 ].
Glyphosate-tolerant B. napus was created using transformation technology to
add two genes, one gene coding for a glyphosate-insensitive target enzyme and
another to detoxify glyphosate to B. napus canola [ 82 ]. Glyphosate tolerance is
currently based on the RT73 transgenic construct; however, new canola cultivars
with a new transgenic construct, MON88302, conferring enhanced tolerance to
glyphosate are currently under development [ 83 ].
Imidazolinone-tolerant B. napus was created using mutagenic treatment of two
genes involved in amino acid biosynthesis to produce enzymes that are no longer
targets for imidazolinone herbicides [ 84 ]. The use of microspore mutagenesis
combined with doubled haploid line development greatly improved the efficiency
of development of imidazolinone-tolerant B. napus [ 85 ]. Herbicide resistance to
imidazolinone herbicides in B. juncea has also been developed [ 84 ] and

patented [ 86 ].
The breeding strategy to develop pod shattering-resistant B. napus canola/
rapeseed uses interspecific crosses of B. rapa or B. juncea to B. napus since both
B. rapa and B. juncea are pod shatter-tolerant species [ 43 , 87 ].
Breeding strategies to improve yield by up to 3.6 % per year (equivalent to a
doubling of seed yield in 20 years) and yield stability have been species specific.
For B. rapa , mass selection and recurrent selection have been used to produce
improved population cultivars of self-incompatible B. rapa [ 10 ]. For B. napus
canola/rapeseed cultivars, breeding for improved seed yield has involved succes-
sively selection within open-pollinated population landraces and crosses of open-
pollinated populations and pedigree selection of derived families, the development