Post harvest diseases fruits and vegetables - Xavier University ...

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
294 Postharvest Diseases of Fruits and Vegetables
Phomopsis, Nigrospora, Fusarium, Epicoccum, Aspergillus, Trichoderma
and others (Snowdon, 1990).
A. Penicillium expansum Link
The blue mold rot, caused by P. expansum, is the commonest and one
of the most destructive rots of harvested apples and pears. Other
Penicillium species, such as P. cyclopium, P. crustosum and P. verrucosum,
may occasionally cause the blue mold rot (Barkai-Golan, 1974; Hall and
Scott, 1989a).
Germinating conidia invade the fruit mainly through wounds or
bruises incited during harvesting and handling. Penetration can also
take place via the lenticels, under favorable conditions (Baker and Heald,
1934), or at the site of infection by other pathogens, such as species of
Gloeosporium, Phytophthora and Mucor (Snowdon, 1990). The
susceptibility of lenticels to penetration is enhanced in over-mature fruit,
during prolonged storage, or by bruising or puncturing (Hall and Scott,
1989a). The fungus produces pale brown to brown soft-watery spots that
enlarge rapidly under shelf life conditions. Under humid conditions,
conidia-bearing conidiophores, grouped to form coremia, are formed on
the surface of the lesion. As the conidia mature, they become blue-green
and form masses which give the decay its typical color. Since decay
development is favored by high humidity, the blue mold is more of a
problem on fruits stored or shipped in plastic film liners (Hall and Scott,
1989a). Decay can progress, albeit slowly, during cold storage; rapid
development begins when the fruits are transferred to warmer
conditions. The fungus can spread during the long months of storage, by
contact between infected and sound fruit, forming 'nests' of decay.
Several strains of P. expansum can produce the mycotoxin patulin
while they develop in apples and pears. The mycotoxin may be highly
toxic to animal tissue and may also display carcinogenic and mutagenic
properties (Stott and BuUerman, 1975). The ability to produce patulin
and the amounts of patulin produced depend on fungal strain, fruit
cultivar, storage temperature and storage atmosphere (Lovett et al.,
1975; Paster et al., 1995). The amounts of patulin produced by different
strains of the fungus in Golden Delicious apples were found to range
from 2 to 100 |ag g^ (Sommer et al., 1974). However, patulin production
by a given strain has also been found to differ at different temperatures
(Paster et al., 1995). Stud5dng patulin production in apples stored under
controlled atmosphere of 1% CO2, 3% O2 at 1°C, Lovett et al. (1975)
reported that only one of the two Penicillium strains tested produced
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