Agriculture Reference
In-Depth Information
morning. Twenty to 30 fl owers can give enough pollen to pollinate 50-60
fl owers. Pollination is done daily, using a small (No. 4) organic hair brush,
so that pollen adheres better to it, or a puf er (Fig. 6.4). Pollen diluted with
Lycopodium
spores (1:1 dilution) allows pollination of more fl owers. About
150 fl owers can be pollinated in 1 h, with a success rate of 80-100% being
achieved.
Hand-pollination is less successful when carried out on very humid,
overcast days and on young vigorous trees. In Honduras, hand-pollinatation
of 'Gefner' atemoya was better when done between 4.00 and 6.00 p.m.
than between 6.30 and 8.30 a.m. when the day temperatures were ~30°C
and relative humidity was low (Duarte
et al.
, 1997). A fruit set of ~47% was
obtained against ~12% for morning pollination. This result was probably
obtained because of the lower night temperatures and higher humidity and the
use of pollen collected in the fi eld and applied immediately. When the Peruvian
'Cumbe' cherimoya was grown in Honduras, better fruit set was obtained
using pollen from a dif erent variety ('Bronceada' from Chile) and afternoon
pollination rather than pollination in the morning (Duarte and Escobar, 1994).
Growth regulators for fruit setting
Hand-pollination in commercial orchards is tedious, time-consuming and
a costly practice. Attempts have been made to use growth regulators, with
considerable variation in the results obtained. Auxin-induced (indole acetic
acid (IAA), naphthalene acetic acid (NAA)) fruit grow very slowly with
less fruit drop, while gibberellic acid (GA
3
) promotes fruit set and growth;
however, it does not aid in early fruit retention (Duarte
et al.
, 1974a; Yang,
1988). Application of the two substances separately at appropriate times has
produced seedless fruit of 200-300 g (Saavedra, 1979). Gibberellin (1000
ppm) is more ef ective than hand-pollination and produced seedless fruit in
atemoya cultivars 'African Pride' and 'Gefner'. Repeated spraying is necessary
to prevent fruit abscission during the fi rst 2 months. Seedless fruit are smaller,
with less fl avour and less fruit splitting than occurs in the seedy fruit that
result from pollination (Yang, 1988). Similar results have been obtained
for cherimoya and sweetsop. GA spraying is not recommended as a general
management practice for atemoya, because of variable results, although it
could be used in areas with poor natural pollination.
Fruit
Fruits of cherimoya, atemoya and sweetsop are compound fruits, generally
conical or roundish or heart-shaped. Cherimoyas can weigh up to 1000 g,
with an average of about 150-500 g, while atemoyas and sweetsops are
smaller. The skin can be smooth with fi ngerprint-like markings or can be
