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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
300 Postharvest Diseases of Fruits and Vegetables
Alternaria infection, including small, black corky lesions, shallow
dark-colored rot, or black decay of the stem (Snowdon, 1990). In addition,
the fungus can penetrate the fruit via open calyces causing core rot of
apples (Ceponis et al., 1969; Combrink et al., 1985). It has also been
reported as a secondary infection of bitter pit, one of the most important
physiological disorders of apples (Ben-Arie, 1975).
Some metabolites of A, alternata strains may be toxic to animals and
humans. Stinson et al. (1981) reported that the main toxins produced by
the fungus during its growth in apples were alternariol and alternariol
monomethyl ether, with maximum concentrations of 5.8 and 0.23 mg per
100 g tissue, respectively. Higher concentrations of both toxins were
produced by another strain of A. alternata^ which was held at 25°C for
several weeks (Ozcelik et al., 1990).
L. Stemphylium botryosum Wallr. [perfect state: Pleospora
herbarum (Pers.) Rabenh.] and Cladosporium herbarum (Pars.)
Link
These two species are weak pathogens that tend to attack weakened or
senescent tissue. C. herbarum is mainly of interest because of its
association with scald and other types of physiological disorders in
various apple cultivars (Edney, 1983), while S. botryosum may attack
lesions resulting from sunscald (Snowdon, 1990). Cladosporium rot has
been found to accompany side rot caused by Phialophora malorum on
pears (Sugar and Powers, 1986). For both pathogens the susceptibility of
the fruit to decay increases during extended storage periods.
M. Trichothecium roseum Link.
Trichothecium is a weak pathogen that invades pome fruit via wounds
or lesions incited by other pathogens. It frequently follows the scab
fungus (Venturia inaequalis) or the black rot fungus (Botryosphaeria
obtusa). It is also one of the fungi involved in the development of core rot
in apple fruits (Raina et al., 1971). The fungus is common under
non-refrigerated conditions since its growth is greatly inhibited below
10°C. The decay is characterized by the production of pink conidia and by
the bitter taste of the infected fruit.
Cultivar Resistance
Since decay pathogens are dependent on the presence of a wound to
initiate infection, resistance of the epidermis (the skin) to breakage may
be an important factor in the resistance of apple cultivars to decay.
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