Annona Species Monograph.pdf - Crops for the Future

Chapter 10. Agronomy
possible to intercrop annonas with annual field or vegetable crops to earn
additional income from the land during the first 2-3 years before annona
production.
The establishment of perennial leguminous or other cover crops, such as
beans, can provide not only additional income, but also avoid soil erosion
and improve the physical structure of the soil. Short grass can be used as a
cover crop in the first 12 months after transplanting (Nakasone and Paull,
1998), although fertilization needs to be modified to supply two crops instead
of one. A wild peanut (Arachis pintoi) is currently being tested at Embrapa
Cerrados Agricultural Research Centre, and has so far been very successful.
Cover cropping may become more important as consumers demand
chemical-free fruit.
10.3.4 Flowering, pollination and fruit set
Annona flowers are hermaphrodite; both female (carpels) and male (stamens)
organs are in the same flower. However, the female part matures before the
male, which is known as dichogamy of the protogynous type. According to
Mansour (1997), there is a short period of stigma receptivity after anthesis,
which is 2-3 h in dry weather. Natural pollination is carried out mainly by
insects, such as Coleoptera (beetles), but is ineffective in several countries
(Saavedra, 1977; Pinto and Silva, 1996; Grossberger, 1999). In Chile, insects
rarely visit a cherimoya flower which suggests that entomophilous
pollination plays only a secondary role in this species (Saavedra, 1977).
Cherimoya is a native species in Chile and should have co-evolved insect
pollinators if it were important.
Although dichogamy and the low population density of pollinator insects are
important limiting factors to successful natural pollination, the effect of
climate and pollen viability seem to interfere greatly with the response to
both natural and artificial (hand) pollination. The effects of these factors may
result in fertilization failure of all or several ovules, resulting in small or
asymmetrical fruits, which obviously affects yield and commercialisation
(Saavedra, 1977). Most annonas flower when atmospheric humidity is low
(Saavedra, 1977), suggesting the importance of humidity in drying out the
stigmas and lowering pollen germination.
Anthesis (flower opening) is most common in the morning or in the evening,
indicating that it is favoured by low temperatures (Mansour, 1997). Studying
the problem of fruit set on custard apple in Dhawar, Egypt, Farooqi et al.
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