Oil Composition Variations - Genetics, Genomics and Breeding of Crop Plants - page 277

mutations. Seiler (2007) focused on genes from wild Helianthus species,
resulting in a continuous improvement in agronomic traits. Interest in using
wild species in breeding programs has increased, but concerns about the
introduction of low oil concentration and quality from the wild species
persist. Two annual desert species, Helianthus anomalus Blake and H.
deserticola Heiser, are excellent candidates for increasing oil concentration
and enhancing quality based on their adaptation to desert environments.
Seiler (2005) reported that the only H. deserticola population collected had
an average oil concentration of 33%, whereas the two populations of H.
anomalus had an oil concentration of 43 and 46%, the highest concentration
recorded in any wild sunflower species. A linoleic acid concentration of
54% in H. deserticola was more typical for a desert environment. The linoleic
fatty acid concentration in the oil of H. anomalus populations was
uncharacteristically high for an Asteraceae and a desert environment,
approaching 70%. Further research will be needed to determine the
inheritance of the fatty acids and oil concentration in annual Helianthus
species to determine whether the traits are transferable to cultivated
sunflower.

8.3 Tocopherols

Tocopherols prevent oil from becoming rancid ( Table 8-1 ) . Sunflower oil is
the richest oil for

-tocopherol (vitamin E). Several tocopherols are found in
the seeds and their antioxidant property is inversely correlated with their
vitamin E activity: -tocopherol, -tocopherol, -tocopherol and -tocopherol

and the vitamin E activity is decreased 10-fold at each step.
Hunter and Cahoon (2007) have defined strategies to enhance vitamin
E in oilseeds. They provided a recent review of tocopherol and tocotrienol
biosynthesis, focusing on branch points and metabolic engineering to
enhance and alter vitamin E content and composition in oilseed crops.
Moreover, a few elements of their biosynthetic pathway are known.

-tocopherol is largely predominant in sunflower oil (95%). Demurin et al.
(1996) have characterized the genetic variability of tocopherol composition
in sunflower seeds developed as isogenic lines in different backgrounds.
They named the genes Tph1 and Tph2 , which undergo natural variation.
They have shown that ' tph1 ' (mutated allele) reduces

- and enhances

-tocopherol. The ' tph2 ' allele reduces -tocopherol and -tocopherol, but

enhances -tocopherol. Together, tph1 + tph2

release an equilibrated set of the four compounds.
Garcia-Moreno et al. (2006) have mapped the Tph1 locus by bulked
segregant analysis on LG 1, enabling further marker-assisted selection and
positional cloning. They performed genetic and molecular analysis of high

-tocopherol with a trace of

-tocopherol content in sunflower. Four sources of high -tocopherol content