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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
324 Postharvest Diseases of Fruits and Vegetables
F. Fusarium spp.
Several Fusarium spp. may cause Fusarium rot of tomatoes, peppers
and eggplants. The most frequently recorded are F. equiseti (Corda)
Sacc, F. avenaceum (Corda ex Fr.) Sacc, F. moniliforme Sheldon, F. solani
(Mart.) Sacc. and F, oxysporum Schlecht (Snowdon, 1992).
The Fusarium spp. are common inhabitants of the soil. The conidia are
dispersed by wind or water, and fruits arriving into storage may already
be contaminated with them. The fungi are weak pathogens that infect
only wounded fruits or those that have been weakened by chilling
temperatures. Fruits stored at too low temperatures for a long time are
particularly susceptible to infection.
The decayed area is usually water-soaked and becomes covered by a
mycelium which may be white, yellow or pinkish, according to the
Fusarium involved. The rot extends into the center of the fruit and the
infected tissue appears pale brown (Dennis, 1983b).
G. Phytophthora infestans (Mont.) de Bary
This fungus induces late blight of potatoes and tomatoes and may cause
serious losses in many areas during wet seasons. Infection is initiated by
the asexual state (sporangia and zoospores), although P. infestans can also
exhibit the sexual state (oospores) (Hermansen et al., 2000).
Disease development depends on weather conditions prior to
harvesting. The optimal temperature for infection is 15-18°C, and wet
conditions are essential for infection capability of the zoospores
(McCoUoch et al., 1982). Infection of leaves, stems and fruits may be by
germinating sporangia or may follow the release of zoospores from the
sporangium (Alexopoulos, 1961). The zoospores, which gain mobility from
their flagella, swim in the film of rainwater on the host. Infection
frequently takes place at the edge of the stem-scar although, under
optimal conditions, direct penetration of the fruit skin can also occur
(Eggert, 1970). Tomatoes harvested from infected fields may be in the
initial stages of infection, when lesions are not yet visible. Such fruits are
packed and decay can occur during transit or at the market.
The infected area is brown, or rusty-tan, hard and with irregular
margins. There is little spreading from diseased to healthy fruit in
transit, in the ripening room or in storage.
H. Phytophthora spp.
Several species of Phytophthora induce Phytophthora rot of tomatoes,
peppers and eggplants, the most common species being P. nicotianae var.
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