Agriculture Reference
In-Depth Information
diploid genoytpes. It is, therefore, not completely female sterile but it is regarded as
commercially sterile in the absence of pollen.
Development of the fruit can be divided into two phases, namely, that which oc-
curs before inflorescence emergence, or the so called 'vegetative apparent phase'
and that occurring after, during the true reproductive phase. The pre-emergence
phase is dominated by peel growth while the pulp does not start to develop until the
fruit re-orientates itself upwards, after emergence. The most rapid development of
the inflorescence occurs during 4-6 weeks prior to emergence. Around the time of
inflorescence emergence the fruit increases rapidly in length. Lassoudiere (
1978
)
has shown that, in the case of the tropical banana AAA (Cavendish subgroup) cv.
'Poyo', there is a rapid increase in finger length for 30 days, which progressively
slows down and is completed in 40-80 days after emergence depending on location
and climate. On the other hand, the increase in fruit diameter is much slower but
continuous until harvest. In the case of cv. 'Poyo' during the first month after inflo-
rescence emergence, the peel represents 80 % of total fruit fresh weight, but after
this period of time, the pulp increases rapidly with the pulp:peel ratio increasing
from 0.17 to 1.82 in 80 days.
At the cellular level, there are 3 main growth stages: (1) rapid cell division from
6 weeks before emergence to 4 weeks after emergence; (2) rapid cell expansion
from 4 to 12 weeks after emergence, and (3) final fruit maturation from 12 to 15
weeks after emergence. These time intervals are only valid under tropical conditions
in which the fruit can be harvested between 85 and 110 days after inflorescence
emergence, but can take considerably longer in the cooler subtropics where fruit de-
velopment can last up to 210 days before harvest. In the case of fruits harvested for
commercial dessert purposes the fact that fruits are normally cut at 'three-quarters
round' must be also taken in account, because at this stage, the fruit angles are still
clearly visible, and the fruit has only reached about 75 % of its potential maximum
size and mass. The final shape and size of a banana fruit (or finger) should be rep-
resentative of the cultivar although there may be an environmental/genetic interac-
tion that determines the eventual size reached at maturity. With the AAA Cavendish
intermediate banana subgroup, the fruit size ranges from 60 to 400 mm, although
larger fruit size differences within this subgroup with other cultivars, such as 'Dwarf
Cavendish' and 'Poyo', can be observed. Genetic variability in fruit size also occurs
within bunches of the same cultivar, with fruits from the distal (bottom) hand usu-
ally 30-40 % smaller than those from the proximal hand. In addition, fruits from the
inner whorl of a hand can be 15 % smaller than those from the outer whorl. Cultural
practices play a role on finger length and explains the reason why multinational
companies normally remove the (distal) bottom two or three hands early in bunch
development in order to maximise finger length on the larger proximal hands.
Papaya
Papaya (Fig.
5.2
) belongs to the small family
Caricaceae
in the Brassicales and is
native to tropical America with the greatest diversity present in the Yucatan-San
