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

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24 Postharvest Diseases of Fruits and Vegetables
Rhizopus stolonifer was consistently capable of infecting the fruit
through existing lesions caused by Colletotrichum and Phomopsis
species. Furthermore, the reduction in the incidence of Rhizopus rot
following fungicidal field sprays was related to the reduced incidence of
field-initiated diseases whose lesions serve as routes of infection for
R. stolonifer.
Penetration due to Tissue Senescence
Tissue senescence during prolonged storage also reduces disease
resistance. Thus, at the end of the storage period, the sensitivity of melon
to the blue-green mold caused by various species of Penicillium and to
the pink mold caused by Trichothecium roseum is increased
(Barkai-Golan, unpublished). A senescencing onion that has commenced
sprouting often harbors base decay, caused by various species of
Fusarium (Marlatt, 1958).
Generally, the rate of decay during storage increases with the duration
of storage as tissue senescence progresses. Increasing the tissue
sensitivity to diseases during storage also contributes to contact-infection
of a healthy product by an infected one covered with spore-bearing
mycelium.
Contact-Infection
Fruits or vegetables that were spared a pathogen invasion via any of
the means of penetration might still be infected during actual storage,
through contact with infected produce. Contact-infection is a significant
factor in the spreading of white watery rot (Sclerotinia spp.) and
bacterial soft rot (Erwinia spp.) in lettuce, cabbage, celery, carrot or
squash during storage. The development of Botrytis in stored
strawberries, which it turns into "mummies" covered with a gray layer of
spore-bearing mycelium, causes a "chain" contact-infection and
jeopardizes the entire basketful of fruit. Similarly, one strawberry or
tomato, or a single grape berry infected by Rhizopus constitutes a focus
from which the decay can spread within the container when it is
transferred from refrigeration to shelf conditions. In fact,
contact-infection by Botrytis or Rhizopus is typical of many fruits and
vegetables, and may account for the major losses caused by these
pathogens during long-term storage. In citrus fruits, contact-infection by
the green and blue mold rots {Penicillium digitatum and P. italicum) is
very common; it often occurs during shipment and can, under certain
conditions, disqualify the entire shipment.
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