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marker loci from this population was used to identify QTLs controlling
fatty acid composition. Three QTLs affecting C18:0 content were identified
on LG 3, LG 11, and LG 13, with all alleles for increased C18:0 content
inherited from CAS-20. These QTLs jointly explained 43.6% of the C18:0
phenotypic variation. On the basis of positional information, the QTL on
LG 11 was suggested to be a
SAD6
locus. The results presented show that
increased C18:0 content in sunflower seed oil is not a simple trait, and the
markers flanking these QTLs constitute a powerful tool for plant breeding
programs.
Pérez-Vich et al. (2006) have also studied the inheritance of high stearic
acid content in the sunflower mutant CAS-3 and CAS-14. In contrast to
CAS-3, high
stearic acid expression in CAS-14 seeds is temperature-
dependent
and not uniformly distributed in the seed. The trait in CAS-3
has
been found to be governed by two genes,
Es
1 and
Es
2. To study the inheritance
of high stearic acid content in CAS-14 and CAS-3, crosses were made with
P21, a nuclear male sterile (NMS) line with a wild type fatty
acid profile. The
genetic analysis included the evaluation
of the F
1
, F
2
, F
3
, BC
1
F
1
, and BC
1
F
2
seed generations. Crosses
between P21 and CAS-14 revealed that the high
stearic acid trait
was controlled by a single recessive gene designated
Es
3.
The analysis of the F
3
and BC
1
F
2
(to P21) generations demonstrated
a
repulsion-phase linkage between the
Es
3 and the
Ms
loci, the
latter conferring
the NMS trait. The frequency of recombination
between
Es
3 and
Ms
was
estimated to be 0.09. Crosses between
CAS-3 and CAS-14 demonstrated that
both lines possess alleles
for high stearic acid content at different loci, as
transgressive
segregants with low stearic acid content were observed in all
generations. Genetic recombination of
es
1 and
es
3 alleles did
not result in an
increment of the maximum stearic acid content
in the seeds compared with
the maximum levels produced by the
es
3 alleles alone. Further studies of
CAS-14 have been done with the
Ol
mutation (high oleic).
Competition assays carried out with CAS-5, a mutant with a higher
content of palmitic acid in the seed oil, indicated that a modified FatA-type
thioesterase is involved in the mutant phenotype (Martínez-Force et al. 2000).
8.2.3 Oleic Acid
8.2.3.1 Oleic Acid in Other Species
Del Río-Celestino and De Haro-Bailón (2007) have studied the inheritance
of high oleic acid content in the seed oil of mutant Ethiopian mustard lines,
obtained by mutagenesis. Oleic acid segregation indicated control of
accumulation by two segregating genetic systems, one acting on chain
elongation from C18:1 to C22:1 and a
fad2
gene involving desaturation from
C18:1 to linoleic acid (C18:2). In addition, C18:1 was influenced by one
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