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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
22 Postharvest Diseases of Fruits and Vegetables
Wood, 1967). Artificial inoculation into the fruit pulp always results in
the fruit being infected, but inserting the fungus into a superficial
scratch in the rind ends with infection only when the fruit is
simultaneously placed under very high humidity. Maximal infection
takes place when the relative humidity reaches 100%. In addition, the
location of the injury is important. Inserting the fungus into the oil
glands of the citrus fruit rind leads to higher infection rates than its
insertion into the rind between the glands.
Wound infection is also characteristic of Rhizopus stolonifer, that
causes watery soft rot in many species of fruits and vegetables; of
Alternaria alternata that causes a dark, rather dry decay in a large
number of fruits and vegetables stored for a prolonged period; of
Geotrichum candidum which causes the sour rot in citrus, melons and
tomato fruits; and of various Aspergillus, Cladosporium and
Trichotecium species, and other storage fungi, in various fruits and
vegetables.
Even pathogens that do not require an injury to facilitate their
penetration - such as various Erwinia species that penetrate potato
tubers through the lenticels, or Monilinia fructicola and Penicillium
expansum, which are capable of penetrating deciduous fruits through
the lenticels - will easily penetrate via wounds. In very much the same
way the Botrytis cinerea fungus, which is capable of penetrating into
young strawberry fruits through the flower parts, or into grape berries
via the style-ends (McClellan and Hewitt, 1973), will penetrate into the
host through an injury. Moreover, blows or pressure on apples or potato
tubers increase the blue mold rot (P. expansum) or the bacterial soft rot
(Erwinia carotovora), respectively, because of an injury inflicted on the
cells around the lenticels - injury that eases the penetration of
pathogens via the lenticels.
Penetration Following Physiological Damage
Physiological damage caused by low temperatures, heat, oxygen
shortage or any other environmental stress, increases the fruit or
vegetable sensitivity and exposes it to storage fungi. The physiological
damage can be externally expressed through tissue browning and
splitting, thus forming locations vulnerable to invasion of wound
pathogens. Yet extreme environmental conditions might enhance
sensitivity to an attack without any visible external signs of damage. A
tomato fruit exposed to chilling temperatures or heat treatments is liable
to be attacked by Botrytis cinerea even when there are no visible
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