Papaya - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 292

along vein margins, and their secretions may aid in pro-
tection against desiccation and/or protection against insect
predators (Ronse et al., 1999). The life of a leaf is 2.5
to 8 months, and new leaves arise at the rate of 1.5-4
per week (Sippel et al., 1989; Nakasone and Paull, 1998).
All parts of the plant contain white latex, including the
unripe fruits.
The flower-bearing stalks arise in leaf axils (Fig. 16.2).
The female flowers, 3-5 cm long, sit alone or in small
groups in the leaf axils and have curvy separate petals; the
ovary is 2-3 cm long and has five fan-shaped stigmas on top.
The male flowers are trumpet shaped with 10 stamens each
and are found on long hanging panicles. Bisexual flowers
are shortly tubular with a midpoint or lower constriction
and the petal lobes larger, have either 5 or 10 stamens,
and some of these tend to become “carpelloid” (fruitlike),
in which case the fruits have a “cat-face” appearance and
are unmarketable. Different types of hermaphrodite flowers
may occur on the same tree, depending on the season or on
the age of the tree (Stambaugh, 1939; Storey, 1958, 1976).
Papaya plants may be self-pollinating (bisexual plants)
or cross-pollinated by insects or wind. Pollinators include
honey bees, wasps, midges, thrips, surphid flies, and but-
terflies. Female plants are less productive and are normally
removed from commercial orchards as soon as they can be
distinguished at flowering.
The fruits are technically classified as fleshy berries
(Villegas, 1997), sometimes called pepo-like berries since
they resemble melons by having a central seed cavity
(Fig. 16.2). They are borne axillary on the main stem,
usually singly but sometimes in small clusters. The fruit
has a smooth exocarp (peel) and thick, fleshy mesocarp
and in shape may be globose, ovoid or pyriform, 7-35 cm
long, and 0.250-10 kg in weight. Female plants produce
medium to large round-shaped fruit of good quality with a
large seed cavity (unpollinated female plants occasionally
set parthenocarpic fruits, lacking seeds); hermaphrodite
plants produce small to medium elongated fruit of good
quality but with a smaller seed cavity; and male plants
with male flowers produce a few, elongated, poor-quality
fruit (Crane, 2008).
Papaya trees bear fruit throughout the year. Yields usually
decline as the trees age and picking becomes difficult. For
those reasons fields are usually replanted or abandoned after
3 or 4 years in commercial production.

color, mating system and growth habit (Manshardt and
Moore, 2003).
Papaya cultivars have been developed by selection of
desired fruit phenotypes (fruit shape, taste, size, flesh color,
firmness, and uniformity) as well as agronomic character-
istics (disease resistance, fruit column compaction, yield)
(Martin et al., 2006; Chan, 2007; Magdalita et al., 2007).
Owing to consumer preference and economic reasons,
fruits from hermaphrodite plants are selected for consump-
tion and market. Female plants are lesser productive than
hermaphrodite; the fruits are lesser marketable because
they do not reach the appropriate size because they are not
well pollinated.
The main papaya cultivars sold as single-serve sizes,
on the EU market are 'Solo,' 'Golden,' 'Sunrise,' and 'For-
mosa' group (Anon, 2009), almost the same as in the United
States: 'Sunrise,' 'Golden,' and 'Solo' (CARICOM, 2006).
Table 16.3 shows the characteristics of the main cultivars
produced over the world. The improvement of cultivars by
breeding programs aims at high yield, low height plants,
fruit with good flesh texture and high sugar content, inter-
mediate fruit size, small fruit cavity and uniformity, and
resistance to pests and diseases.
Mountain papaya ( Vasconcellea pubescens also known
as Carica candamarcensis, Carica cundinamarcensis, or
Carica pubescens ) is a papaya relative native of the An-
dean range from Panama to Bolivia were can be seen
growing at altitudes between 5,000 and 9,000 feet. The
plant looks quite similar to the common papaya but is rela-
tively smaller and less branched. Fruits are obovoid turning
yellow or orange at maturity. Mountain papaya ( Vascon-
cella pubescens ) cross with Vasconcella stipulata resulted
in 'Babco' hybrid, widely cultivated for fruits in South
America (Morton, 1987; Badillo, 1993).

HARVESTING, POSTHARVEST HANDLING,
AND STORAGE
Well-cared-for plants may begin to produce flowers
4 months after planting and fruit 7-11 months after plant-
ing. The amount of fruit produced by a papaya plant varies
with the general climate, weather conditions during the
year, and plantcare. Yields vary from 27 to 36 kg per tree
over a 12-month period depending on the cultivar (Crane,
2008). In some papaya cultivars, flower and fruit thinning
are necessary to remove the most defective and to distribute
the fruits to avoid damage to each other.

MAJOR CULTIVARS
Undomesticated papaya was a spindly plant with nearly
inedible fruits. During domestication the species have
undergone considerable changes in fruit size, fruit flesh

Harvesting
Papaya fruits should be harvested when the color of the
skin changes from dark green to light green and when one