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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
CHAPTER 8
MEANS FOR MAINTAINING HOST RESISTANCE
It was previously pointed out that fruits become more susceptible to
invasion by postharvest pathogens as they ripen (see the chapter on
Factors Affecting Disease Development - The Fruit Ripening Stage).
Treatments and conditions that lead to delayed ripening and senescence
can, therefore, indirectly suppress postharvest disease development. These
include low-temperature storage, I0W-O2 and high-C02 atmospheres,
ethylene removal from the atmosphere, growth regulators, calcium
application; these as well as other treatments or strategies may contribute
to maintaining the natural resistance typical of the young fruit or
vegetable.
A. COLD STORAGE
Storage at low temperature is the main method for reducing
deterioration of harvested fruits and vegetables. The importance of cold
storage in decay suppression is so great that all other control methods
are frequently considered as supplements to refrigeration (Eckert and
Sommer, 1967).
Low temperatures affect both the host and the pathogen
simultaneously. They prevent moisture loss from the host tissues and
consequent shriveling; they retard metabolic activity and delay
physiological changes that lead to ripening and senescence. Since fruits
and vegetables become generally more susceptible to pathogens as they
mature and approach senescence, the retardation in the physiological
activity of the host is accompanied by a delay in decay development after
harvest. As with the host, the metabolic activity of the pathogen is also
directly influenced by the environmental temperature, and both its growth
ability and enzymatic activity can be greatly retarded by low temperatures.
Low temperatures can thus delay postharvest disease development in two
ways: (a) indirectly, by inhibition of ripening and senescence of the host
and extension of the period during which it maintains its resistance to
disease; and (b) directly, by inhibition of pathogen development by
subjecting it to a temperature unfavorable for its growth.
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