Annona Species Monograph.pdf - Crops for the Future

Chapter 9. Genetic Improvement
Shoot proliferation of sugar apple was achieved with hypocotyls and nodal
cuttings growing in Woody Plant Medium, supplemented with BAP and
silver thiosulphate to control leaf abscission (Lemos and Blake, 1994; 1996
a, b). Rooting was obtained when shoots were preconditioned in medium
with activated charcoal, and then treated with NAA or IBA (Lemos and
Blake, 1996 b). To improve rooting, they used galactose instead of sucrose in
the rooting medium. Eighty percent of the plantlets were successfully
acclimatized in the greenhouse (Lemos and Blake, 1996 b). This
methodology now needs to be transformed into a commercial protocol.
However, the greatest success in annona micropropagation was obtained in
cherimoya. Encina et al. (1994) described in vitro morphogenesis of juvenile
cherimoya and achieved a micropropagation system for adult cherimoya
materials, obtaining 50% rooting and exceptionally good acclimatisation
(Encina et al., 1999). To increase the success of acclimatisation, Azcòn-
Aguilar et al. (1994) inoculated cherimoya with arbuscular mycorrhizal fungi
to improve growth, survival and development of cherimoya produced in
vitro. Currently they are working on several methodologies (Encina et al.,
1999): a) somatic embryogenesis; b) adventitious organogenesis and cellular
cultures; c) ploidy manipulation; d) autotrophy induction; and e) genetic
transformation. However, the authors did not mention that these
methodologies have already been applied commercially.
Although there are numerous experimental protocols for Annona tissue
multiplication, the final price of the plantlets is still too high for commercial
use. Given the potential of this technology, further research is needed to
transform experimental protocols into commercial protocols.
9.5.2 Genetic transformation
Encina et al. (1999) have started studying genetic transformation of
cherimoya, mainly to optimize the protocol for Agrobacterium
transformation. The objectives are to control ripening, to change post-harvest
characteristics, and to provide pest and disease resistances. For other Annona
species there are no advanced studies.
9.5.3 Molecular markers
Samuel et al. (1991) suggested the use of allozymes to study diversity and
systematics in Annonaceae. They considered these systems to be efficient for
investigations of the origin of polyploids for breeding programmes. A
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