Oil Composition Variations - Genetics, Genomics and Breeding of Crop Plants - page 275

position (Bervillé et al. 2004). However, broadly, there is a good fit between
the two maps in the MOD region. Bervillé et al. (2004, 2005) have found the
ATT SSR in the intron of the MOD . The SSR polymorphisms (four alleles)
are very useful to map the locus and to follow linkage disequilibrium with
the Pervenets insertion. Tang et al. (2006) have shown that the ORS1180 is
tightly linked to the Pervenets locus, but there are still many recombination
events that are worrisome for breeding.
8.2.4 Linoleic and Linolenic Acids
8.2.4.1 Linoleic and Linolenic Acids in Other Species
Linoleic acid content is an alternative to oleic acid content as we have shown
for sunflower and other crops. High linoleic acid oil for industry could be of
value, but when over 70% in seed oil, plant growth seems affected.
In soybean, Wang (2006) has found one plant containing zero linolenic
acid content with the half-seed method in the strain 0358. It was the first
report of a zero linolenic acid soybean. The material will be very useful for
breeding cultivated varieties with low linolenic acid content and especially
for studying gene action for linolenic acid in soybean by the aid of
biotechnology.
Poneleit and Alexander (1965) have studied the inheritance of linoleic
and oleic acids in maize. Their results suggest that desaturation of stearic
acid to oleic acid is under simple Mendelian control. High linoleic acid
content is recessive to low linoleic acid.
When linolenic acid content is too high in the oil, it becomes easily
oxidized, and it is unstable. Moreover, the ratio C18:3 to C18:2 and C18:1 in
the diet may cause health disorders. This is the case in soybean and rapeseed
oils. Silva-Gesteira et al. (2003) have studied the inheritance and the nature
and magnitude of gene effects on soybean seed linolenic acid level. They
crossed an accession BARC-12 (low linolenic acid content) with a commercial
Brazilian cultivar CAC-1 (normal linolenic acid content). Means and
variances of F 1 , F 2 , and F 3 generations have been studied and results
demonstrate that linolenic acid content in soybean is under the genetic
control of a small number of genes.
Scarth and Tang (2006) have modified Brassica oil using conventional
and transgenic approaches. The conventional approach to fatty acid
modification has explored natural or induced mutations occurring in the
same plant species or close relatives within the Brassica genus. These
mutations have been shown to be associated with a few enzymes in the
biosynthetic pathway of the fatty acids. Several types of Brassica oil with
significantly altered levels of the long chain fatty acid, viz., erucic acid (C22:1)
and medium chain fatty acids such as oleic acid (C18:1) and linolenic acid