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LG 14 (peak LOD 5.1), in the same position as the major QTL for C18:1 in
this population. This QTL accounted for 19.3% of the C18:0 phenotypic
variation. The CAS-3 allele increased the level of C18:0 at all the putative
QTLs, apart from the one on LG 8, where it decreased it.
QTLs affecting C18:1 concentration were identified on LGs 1, 8, and 14
in the HAOL-9×CAS-3 population. These QTLs together explained 58.4% of
the phenotypic variance for this trait. The major C18:1 QTLs accounted for
56.5% (LG 14; peak LOD 19.7) and 24.5% (LG 1; peak LOD 8.5) of the
phenotypic variance in C18:1. HAOL-9 alleles for the QTLs on LG 1 and LG
14 increased the C18:1, whereas the CAS-3 allele for the QTL on LG 8
increased the C18:1 levels. An oleoyl-PC desaturase locus (OLD7) was found
to cosegregate with the gene
Ol
controlling high C18:1 on LG 14.
Sunflower seed composition is largely influenced by environmental
factors, such as water availability and temperature. Severe water deficit
during the reproductive stages decreases the oil content in sunflower (Nel
et al. 2002). Water deficit from sowing to the end of anthesis modifies the
fatty acid composition of standard hybrids (Roche et al. 2006). Severe water
deficit during seed filling decreases oleic acid (OA) by 10-16%, with a
concomitant increase of linoleic acid (LA), in standard hybrids of sunflower
(Roche et al. 2006). Ebrahimi et al. (2008) identified QTLs controlling oil
content and quality (palmitic, stearic, oleid and linoleic acide content) under
different water regimes in RIL population of the cross PAC2×RHA266
et al. 2007a) was used for this study. Oil content, palmitic acid, stearic acid,
oleic acid and linoleic acid contents were investigated in the greenhouse
and field conditions each under well-watered and water-stressed treatments.
A wide range of phenotypic variation and transgressive segregation were
observed for all the traits under different water regimes. Oil content was
negatively correlated with stearic acid and oleic acid in both well-watered
and water-stressed conditions in the greenhouse and field. It was positively
correlated with palmitic acid and linoleic acid. Twelve, eight, six and three
QTLs were identified for oil content in greenhouse well-watered, greenhouse
water-stressed, field well-watered and field-water-stressed conditions,
respectively. The total percentage of phenotypic variance explained by these
QTLs were >100%, 90%, 66% and 34%, respectively. No explanation was
given for the R
2
> 100%, but it could be attributed to the limited number of
RILs used in their study, which leaded to overestimation of individual R
2
.
Although the parental lines did not differ for oil content in all four growth
conditions but alleles transmitted from the PAC2 parent increased the oil
content for 22 QTLs and the parent RHA266 contributed to favorable alleles
of only seven QTLs out of 29 QTLs detected for oil content in the four growth
conditions.
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