Vitamins in Fleshy Fruits - Fruit Ripening: Physiology, Signalling and Genomics - page 140

roles in plant development and metabolism
and in protection against various stresses.
They are therefore under tight regulation
by environmental conditions (Roselló et
al. , 2011; Massot et al. , 2012), especially
light, which may exert a strong stress effect
on plants. Temperatures during fruit
growth may also affect fruit content in
vitamin C and provitamin A (Gautier et al. ,
2008). As a consequence, climatic con-
ditions and cultural practices can be
adapted to modify the fruit contents in
provitamin A, vitamin E and vitamin C.
This can be achieved by modulation of the
amount and quality of light during fruit
growth and ripening, for example by
cultivating plants in different growing
seasons or at different altitudes, or through
the control of irradiance by light-emitting
diodes in the greenhouse (Ma et al. , 2012)
or photoselective nets in open fi elds
(Shahak et al. , 2006). These strategies can
be applied commercially to increase fruit
provitamin A (e.g. E -cryptoxanthin in
citrus fruits; Ma et al. , 2012), as they will
improve the nutritional value of the fruit
and its visual appearance at the same time.
Modulating fruit vitamin E and C content
by technological means can be more
challenging, unless the increase in
nutritional value is suffi cient to bring
signifi cant added value to the fruit product.
Fruit vitamin content can also be
controlled at subsequent steps, during
postharvest storage and/or during fruit
processing. Storage can lead to substantial
losses in vitamins, especially in vitamin C
(Stevens et al. , 2008; Cruz-Rus et al. , 2011).
The various methods used to extend fruit
shelf-life will have an impact on the fruit
micronutrient content, for example in
strawberry and mango (Rivera-Pastrana et
al. , 2010; Yang et al. , 2010; reviewed by
Lee and Kader, 2000), especially when
their synthesis is regulated by hormones
and/or fruit ripening. Likewise, cooking or
thermal treatments and subsequent storage
of the processed product will result in
signifi cant reductions in some vitamins,
such as the provitamin A E -carotene,
vitamin E and vitamin C (Abushita et al .,

2000; Koh et al ., 2012), although the
processed fruit product may still retain
signifi cant amounts of vitamins (e.g. 45%
of the initial content of vitamin C in tomato
paste; Abushita et al ., 2000). As an
alternative to conventional thermal treat-
ments, new methods such as high-pressure
or microwave preservation will help retain
the initial content of vitamins in processed
products (reviewed by Barrett and Lloyd,
2012). In addition, disruption of fruit
chromoplasts by processing and con-
stitution of emulsions may increase the
bioaccessibility of carotene (Svelander et
al ., 2011).
In recent years, most efforts have been
focused on the genetic improvement of
vitamin content in fruits, and especially in
tomato, a model fl eshy fruit; whilst tomato
is only moderately rich in carotenoids and
vitamins E and C, this fruit species has a
widespread consumption throughout the
world, therefore contributing in a large way
to human dietary nutrition. Other well-
studied species are mango (rich in
carotenoids and vitamin E), papaya
(carotenoids), palm fruit (carotenoids and
vitamin E), apricot (carotenoids), strawberry
(vitamin C), kiwifruit (vitamin C) and apple
(vitamin C). Species such as mango
represent seasonally important sources of
vitamins in some tropical countries whose
inhabitants suffer chronically from vitamin
defi ciency (FAO/WHO, 2004).
Improving vitamin content in fruit
through genetic means is a realistic goal
because: (i) our understanding of plant
biosynthesis pathways and of the
regulation of carotenoids and vitamins E
and C has progressed considerably in
recent years (Hirschberg, 2001; Linster and
Clarke, 2008; Fraser et al. , 2009; Mène-
Saffrané and DellaPenna, 2009; Almeida et
al. , 2011; Fitzpatrick et al. , 2012); and (ii)
genomic tools, such as marker-saturated
genetic maps, genome sequences and other
genetic resources, are now available for
most crop species, allowing easier
identifi cation of alleles that improve
vitamin content and their introduction into
elite varieties.