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

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CHAPTER 2
POSTHARVEST DISEASE INITIATION
A. THE PATHOGENS
Upon harvest, ripe fruits and vegetables become subject to attacks of
various microorganisms incapable of attacking earlier in the course of
growth in the field. These are largely weak pathogens, fungi and
bacteria, typical of the harvested and stored fruits and vegetables.
Disease resistance, which was embodied in the plant organ designated
for storage during its developmental stages on the plant, weakens as a
result of separation from the parent plant. In addition, picked fruits and
vegetables are rich in moisture and nutrients, which suit the
development of pathogens. Upon ripening the fruits and vegetables often
become more susceptible to injury and, therefore, more susceptible to the
attack of those microorganisms that require an injury or damaged tissue
to facilitate their penetration (Eckert, 1975). Moreover, during the
prolonged storage of fruits and vegetables a series of physiological
processes occurs which leads to the senescencing of the vegetal tissues
and, in parallel, to their increased susceptibility to weak pathogens that
attack senescencing vegetal tissues.
B. THE ORIGIN OF THE PATHOGENS
Fungi and bacteria responsible for in-storage decay often originate in
the field or the orchard. When penetration into the host takes place in
the field, the pathogen, which is then in its early or quiescent stages of
infection, will get to the storeroom within the host tissue without
eliciting any symptoms of decay. Yet, even when preharvest infection has
not taken place, there are always fungal spores and bacterial cells, which
are typical components of the airborne microorganism population, on the
fruit and the vegetable during their growth. This cargo of spores and
cells is transferred to storage with the harvested fruits and vegetables.
Examination of the fungal spore population on the surface of stems,
leaves, flower parts, fruits and other plant organs, after harvest, reveals
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