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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
282 Postharvest Diseases of Fruits and Vegetables
2. Stem-End Pathogens
Stem-end rot is a very serious postharvest disease of mango,
responsible for heavy losses during transit and storage. The fungi
involved in stem-end rots are mainly: Botryodiplodia theobromae Pat.
[perfect state: Physalospora rhodina (Berk. & Curt.) Cooke], Phomopsis
spp. and Dothiorella spp. In their asexual state - pycnidia with conidia -
they persist in the orchard on dead wood. The sexual state (perithecia
and ascospores) is also occasionally exhibited (Alvarez and Lopez, 1971).
The conidia are washed down by rainwater, thus contaminating the fruit.
Stem-end rots arise by invasion of the cut stem of the fruit at harvest or
shortly after harvest (Pathak and Srivastava, 1969), but may originate at
injuries in other locations on the fruit. The rot develops rapidly at room
temperature, causing a soft-watery decay, which involves the whole fruit
within several days, and is characterized by the development of minute
black pycnidia over the lesions.
3. Alternaria alternata (Fr.) Keissler
This fungus usually develops from quiescent infections on the surface
of mango fruits, where it creates typical black spots. Germinating conidia
can penetrate the immature fruit via lenticels but infection remains
quiescent until the onset of ripening after harvest (Prusky et al., 1983).
The resistance of young mango fruits to fungal development has been
related to the presence in the peel of fungitoxic concentrations of
antifungal resorcinol compounds (Droby et al., 1986).
Control Measures
The major strategies for control of postharvest diseases of mangoes
include regular sprays in the plantation, to reduce quiescent infections of
C. gloeosporioides, Anthracnose can be controlled by immersing
mature-green fruits in hot water at 55°C for 5 min after harvest, but this
treatment does not satisfactorily control Diplodia stem-end rot (Spalding
and Reeder, 1978). The heat treatment may slightly injure the fruit and
accelerate the change in peel color from green to yellow. The addition of
various fungicides to the hot water enabled the concentration of the
fungicide and the level of the heat treatment to be reduced compared
with those required when either was applied alone, resulting in improved
control of anthracnose and stem-end rot (Spalding and Reeder, 1986b)
and, in turn, a greater amount of fruit acceptable for marketing.
The efficiency of quarantine heat treatments (developed for fruit fly
disinfestation in mangoes) as a means for postharvest disease control,
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