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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
126 Postharvest Diseases of Fruits and Vegetables
Indirect Effects on Pathogen Development
It is well known that susceptibility of fruits to postharvest decay
organisms generally increases with ripening. A controlled atmosphere
may retard ripening and senescence processes of fruits and vegetables,
through the suppression of respiration and other metabolic functions.
Low O2 levels and high CO2 levels may also affect ripening by retarding
or inhibiting the production and activity of ethylene, whose accumulation
at certain levels in the storage atmosphere may result in the initiation of
ripening or the enhancement of tissue senescence in fruits (Yang and
Hoffman, 1984).
A study carried out by Aharoni et al. (1986) showed that ethylene
played a primary role in the initiation of broccoli inflorescence
senescence, and that the senescence-retarding effects of a C02-enriched
atmosphere were related to its ability to block ethylene action.
Furthermore, the marked decrease in rot development observed in
broccoli florets inoculated with Botrytis cinerea spores and stored in a
C02-enriched atmosphere, was completely nullified by the addition of 10
ppm ethylene to the atmosphere (Table 9).
Removal of ethylene from long-term CA storage also delayed ripening
in certain cultivars of apples, as expressed by improved firmness
retention. This was especially apparent in fruit picked in its
preclimacteric state (Knee, 1990). Along with the prolongation of the
physiological life of apples, these conditions also led to decay suppression
during storage (Bompeix, 1978; Sams and Conway, 1985).
TABLE 9
Effect of CO2 and ethylene on decay development in broccoli florets
inoculated with Botrytis cinerea spores^
^ Index of decay^
(after 120 h of incubation)
Air 4.0
CO2(10%) 2.6
C2H4 (10 ml 1-1) 4.2
CO2 + C2H4 4^2
1 From Aharoni, N., et al., (1986)
2 1, no decay; 5, maximum decay development
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