Agriculture Reference
In-Depth Information
than those resulting from insect-pollinated flowers. Due to the short longevity of
cherimoya pollen, growers have to collect pollen daily to perform hand pollination
although recent results indicate that pollen can be stored at low temperatures for
several months (Lora et al.
2006
).
In order to increase the commercial value of cherimoya and other species in
the genus, a common objective in most breeding programs is the reduction in the
number of seeds in the fruit. The possibility of producing seedless cherimoya cul-
tivars has been recently put forward thanks to molecular work that has allowed the
identification of a key gene involved in ovule and seed development in the genus
Annona
(Lora et al.
2011b
).
In Spain, the cherimoya blooming season commences in late May and lasts through
July whereas the regular harvesting season extends from October to December. How-
ever, under appropriate cultural practices (that mainly involve pruning before the
blooming period), it is possible to induce flowering in August through to early Sep-
tember; the fruits set by those late flowers overwinter in the tree and can be harvested
over March-April. This same approach can be used in other regions with similar
environmental conditions in order to extend the commercial harvesting season.
Avocado
The avocado (Fig.
5.4
) belongs to the Lauraceae, a family included in the order Lau-
rales and, together with the orders Canellales, Magnoliales and Piperales, form the
Magnoliid clade in the basal angiosperms (Soltis et al.
2005
). More that 50 genera
and a variable number of species (ranging from 2,500 to 3,000) distributed along
tropical and subtropical regions of the world are included in the Lauraceae.
The center of origin of avocado can be placed in an area that ranges from the eastern
and central highlands of Mexico through Guatemala and to the Pacific coast of Cen-
tral America (Popenoe
1976
). Archaeological records suggest that selection and use of
this crop took place in Mexico at least 10,000 years ago (Knight
2002
; Galindo-Tovar
et al.
2008
).
Persea americana
consists of at least 8 botanical varieties or subspecies
of which three, also called horticultural races, have agronomic significance: West In-
dian (
P. americana
var
. americana
), Guatemalan (
P. americana
var.
guatemalensis
)
and Mexican (
P. americana
var.
drymifolia
) (Scora et al.
2002
) (Table
5.5
). The three
horticultural races show no inter-race sterility barriers and most currently cultivated
commercial varieties, such as 'Hass' and 'Fuerte', are inter-race hybrids. The crop is
currently widely distributed in regions with subtropical and tropical climates.
Edaphoclimatic Requirements for Production
Soil Requirements
Avocado can be cultivated in a wide range of soils from volcanic to sandy loam and
calcareous soils. Optimum pH values range from 5 to 7 and pH values above 7.0
