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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
316 Postharvest Diseases of Fruits and Vegetables
A. Botrytis cinerea Pers. [perfect state: Botryotinia fuckeliana (de
Bary) Whetzel]
The gray mold rot caused by B, cinerea is the most important disease
of grapes, and can cause very heavy losses in all grape-producing
countries, especially after wet seasons (Pearson and Goheen, 1988).
The fungus persists in the soil and can be found in infected vines and
on decasdng plant material. The pathogen exhibits both the sexual state
(apothecia with ascospores) and the conidia, which are the asexual state
(Snowdon, 1990). Both sporulation and infection take place under wet
conditions. When late-harvested grapes have been exposed in the field to
high humidity, dew and rainfall, a blossom infection may occur; the
fungus develops a quiescent infection in the young developing fruits that
cannot be eradicated by the SO2 treatment (Eckert and Ogawa, 1988).
The fungus resumes activity when the fruit matures (Marais, 1985).
Thus, grapes which were apparently sound when harvested and packed
may develop rotting only at a later stage (Nelson, 1956). Secondary
infection spreads by contact during storage, resulting in the formation of
'nests' of decay among the grapes.
Decay is manifested by a brown discoloration, which later becomes
covered with an abundance of gray-brown spores (Marais, 1985). Under
humid conditions, a sporeless mycelium is developed.
B. Cladosporium herbarum (Pers.) Link
This species is the cause of Cladosporium rot in stored grapes. It is an
important cause of spoilage because of its ability to develop in grapes in
cold storage.
The pathogen has frequently been reported as the most important
airborne fungus (Gregory, 1973). Primary infections occur before harvest.
The fungus is capable of penetration through the intact fruit or at the
blossom end of the berry and infection is favored by wet seasons (Hewitt,
1974). The disease is characterized by circular black spots or lesions
which, after removal to shelf-life conditions, become covered with
olive-green conidia-bearing mycelium. The decay is shallow and does not
extend to the seeds. The affected tissue is attached to the skin and can be
removed with it (Harvey and Pentzer, 1960).
C. Alternaria alternata (Fr.) Keissler
This fungus develops on dying flowers that then become a source of
airborne spores. Infection can occur on any part of the fruit but is often
initiated at the stem end. Disease initiation and development are favored
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