Oil Composition Variations - Genetics, Genomics and Breeding of Crop Plants - page 269

Since the progenies of a cross between a low oleic and a high oleic line
segregated as continuous for oleic acid content (as a quantitative trait)
depending on the population size and the oleic acid distribution of F 2 plants,
and considering the dominance of the HO trait, authors have made two
(3HO:1LO), three (1HO:2Mid:1LO), or more classes for oleic acid content.
This implies a number of loci. All the studies have been reviewed in Lacombe
and Bervillé (2000).
However, by the year 2000, individuals that carry the Pervenets mutation
could not be identified. Thus, the studies dealt unambiguously with the
inheritance of the HOAC trait. Authors tried to determine the locus that
produced the main effect, which should be the locus at which the mutation
has occurred, in comparison to the effect of loci with other minor effects,
also called modifiers.
Lacombe and Bervillé (2001) have shown for the first time that the HOAC
in half-cotyledons and a rearrangement in an oleate desaturase cosegregated
(genetically linked) in an F 2 population of a cross between a LO with a HO
line. Only the kernels that carried the Pervenets rearrangements displayed
HOAC as high as 90%, compared to 83% in the female parent. However,
many kernels without the Pervenets mutation displayed a range of variation
for oleic acid content from 15 to 50%, although the LO maternal line was
fixed at 28% oleic acid.
Only one QTL approach to the inheritance of HOAC has been published
(Perez-Vich et al. 2004). It followed both the stearic and the oleic acid content
in F 2 progenies. Each trait, high stearic and high oleic acid content displayed
QTLs in the regions of a stearoyl- and oleoyl- desaturase, respectively. Other
minor QTLs have been supposed corresponding to alternate pathways
(thioesterase acyl carrier protein) (Pérez-Vich et al. 2004, 2006).
It is clear from all these studies that all HO lines carry the same Pervenets
mutation. In contrast, other types of factors also act on the oleic acid content,
such as the genetic backgrounds and modifier genes that have not yet been
elucidated.
8.2.3.2.3 Expression Induced Changes by Pervenets Mutation
Since the enzymatic function of the oleate desaturase has been shown to be
lacking in HOAC sunflower, Kabbaj et al. (1996b) studied whether the
corresponding transcript is present or not. The oleate desaturase was first
cloned in Arabidopsis by Arondel et al. (1992) and later cloned in other plant
species. Unfortunately, the sunflower transcript did not display enough
homology with Arabidopsis to be cloned directly. A cDNA library was
constructed from developing sunflower embryos and probed by stearate
desaturase cDNA and oleate desaturase cDNA from diverse species. Only
with a stearate desaturase cDNA and a partial oleate desaturase clone from