Agriculture Reference
In-Depth Information
more tolerant to low temperatures than other species in the genus. Temperatures
above 30 °C can result in pollination problems and can cause leaf and fruit burn as
well as increase the drop of recently set fruits (Farré et al.
1999
; Van Damme et al.
2000
). Temperatures below − 2 °C can produce damage to leaves, fruits and trunks
(Farré et al.
1999
).
Crop Management
The cherimoya is a semi deciduous fruit tree with simple leaves arranged alternately
that must abscise before bud development takes place, since axillary buds are en-
closed inside the leaf petiole (Schroeder
1941
). The leaves of the cherimoya abscise
just before the blooming period. Flowers appear as single or small 2-4 flower clus-
ters on a short peduncle on the current season's growth (Cautín and Agustí
2005
). In
Spain, the tree is pruned in an open vase system with 3 of 4 main branches. Before
the new growth starts, fruit branches and the growing point of main branches are
removed and, during the period of active growth, suckers are eliminated or removed
from the tree (Farré et al.
1999
). Commercial propagation is usually carried out by
grafting onto seedling rootstocks (George and Nissen
1987
) and no clonal root-
stocks are commercially available.
Reproductive Biology
Flower Development
Cherimoya, like most species in the Magnoliales, has hermaphroditic flowers, with
a pyramidal gynoecium and an androecium surrounded by two whorls of 3 petals;
the internal whorl is small and scale-like whereas the external whorl is greenish and
fleshy. Consequently, the flowers of
A. cherimola
are herkogamous with a spatial
separation between the androecium and the gynoecium and a non-functional zone
of carpels that lay above the anther rows that establish a clear boundary between
the male and female organs of the flower (Lora et al.
2011a
). The gynoecium is
composed of up to 300 fused carpels (each containing a single ovule), forming a
syncarp that occupies the centre of the conic receptacle. The androecium is located
below the gynoecium and forms a helicoidal structure with up to 200 stamens. The
cherimoya flowering cycle is characterised by a protogynous dichogamous system
(Wester
1910
), a common characteristic in Annonaceae (Gottsberger
1999
) an in
other early-divergent angiosperm lineages with hermaphrodite flowers (Endress
2010
); in species showing protogynous dichogamy, the female function matures
before the male function, generally preventing self-fertilization in the same flower.
Moreover, flowers of the same genotype usually open synchronously and, conse-
quently, transfer of pollen between different flowers of the same genotype is dif-
ficult (Lora et al.
2010
).
