Agriculture Reference
In-Depth Information
Some trials have been made to enhance fruit set in cherimoyas and
atemoyas. Auxins will reduce fruit drop while gibberellins will improve fruit
set and growth rates. In some trials seedless fruits of atemoya have been
obtained, but repeated sprays have to be done during the fi rst 2 months and
fruit size is smaller and fl avour is poorer. Similar results have been obtained
with cherimoya and sweetsop. None of these practices are commercially used.
In guava, trials have been done to reduce the number of seeds with auxins
and gibberellic acid; the latter has reduced the number of seeds and enhanced
soluble solids but is not used commercially.
In commercial pineapple production, fl ower induction is carried out to
obtain more uniform fl owering. The plants are sprayed, once they achieve the
right size, with ethylene gas dissolved in water or ethephon (2-chloro-ethyl
phosphonic acid), an ethylene-releasing compound. Also, acetylene generated
from calcium carbide reacting with water can induce fl owering; this product
can be applied dissolved in water as a spray or by putting a little amount of
it in the cup formed by the leaves in the centre of the plant. Since ethylene is
the ripening hormone that plants and fruits produce naturally, many fruits
are treated with ethylene gas or ethephon to hasten and to obtain uniform
ripening. This is done commercially with bananas. For citrus, it helps achieve
better rind colour.
Some growth retardants, such as pachlobutrazol and uniconazole,
which act as gibberellin antagonists, are used commercially to prevent
mango shoots from re-sprouting too soon. This treatment allows the shoot
to achieve a minimum age, so that when it does sprout it is a fl ower panicle
instead of a vegetative shoot. These products have not been approved by the
US government but are used outside of the USA.
Potassium nitrate or ammonium nitrate is used to induce fl owering in
mango. This foliar application treatment is more successful if the shoots have
achieved certain age and are mature. This treatment is more successful in the
tropics than the subtropics. In the case of longan, potassium chlorate can be
applied to the soil to induce fl owering. Dinitro-orto-cresol (DNOC) has been
used to burn mango infl orescences in order to force a second fl owering a few
weeks later, when climate or market conditions are more suited.
POLLINATION
Some fruit species have self-sterility problems and will not produce good yields
in single-variety planting. The species can be completely or partially self-sterile
or the plants can have dif erent sexes or because of dichogamy, when there is
no coincidence of the maturation time of the female and male organs of the
fl owers. Often more than one genotype has to be present in the fi eld or artifi cial
pollination has to be done. In other cases, a certain number of male plants
have to be inter-planted among female plants. For avocados that have A and
