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Composition of tomatoes and tomato products in antioxidants (WG1) page 17
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4.1 Breeding
In a breeding programme it is possible to accumulate the genes that increase the
lycopene content and to eliminate those genes that decrease the lycopene content. There are
several ways to accomplish this:
First of all, it is very important to have a good genetic base to start with. All the
desired agronomic treats need to be available in the breeding nursery. Incorporation of the
genes that increase lycopene content and elimination of genes that decrease the lycopene
content can be done by pedigree selection and backcross programme. That this approach can
be successful has been proven by the Israelian company LycoRed. Together with the Volcani
Institute they developed hybrids with 3 or 4 folds content of lycopene in tomato fruits.
During natural or breeding selections, certain mutations can be produced on genes
which regulate the synthesis of enzymes in the metabolism of carotenoids. For example, the
mutants t accumulate the metabolic precursors of lycopene : phytoene, and ζ-carotene but
contain no lycopene (Table 5) (Tomes 1963).
Table 5- The carotenoid composition of tomato mutants (g/kg dry matter)
Mutant Phytoene Lycopene β-carotene ζ-carotene δ-carotene
normal 2.9 4.4 0.5 - -
r 1.0 - trace - -
t 5.1 - 0.1 4.5
del 1.3 1.7 0.6 0.1 3.3
hp 1.5 5.6 0.7 - -
og 2.5 5.0 0.3 - -
After Tomes 1963.
In this case, the phytoene desaturase is apparently absent from the fruit. The mutant
Del accumulates mainly the δ-carotene which is an intermediary in the synthesis of carotene.
Certain types tested, for example the mutant hp, accumulate lycopene. This can either be the
consequence of over-expression of phytoene desaturase (lycopene synthesis) or of repression
of lycopene cyclase (β-carotene synthesis).