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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
174 Postharvest Diseases of Fruits and Vegetables
storage, while the fresh appearance of the fruit was maintained. A trial
shipment of 'Galia' melons by sea transport from Israel to Europe
demonstrated that sodium bicarbonate incorporated into a wax coating
maintained the marketability of the fruit. It was suggested that this
biocide could serve as an alternative to imazalil, which had been
incorporated into the wax until recently, to control decay during
prolonged storage (Aharoni et al., 1997).
Since Helminthosporium solani, the causal agent of silver scurf in
potato tubers, developed resistance to benzimidazole compounds,
postharvest losses attributed to this disease have increased and no
fungicide is currently registered for its control in the United States
(Olivier et al., 1998). Looking for alternative antifungal compounds for
suppression of silver scurf on potatoes, Olivier et al. (1998) evaluated the
effectiveness of several organic and inorganic salts on H. solani
development; they found that potassium sorbate, calcium propionate,
sodium carbonate, sodium bicarbonate, potassium carbonate, potassium
bicarbonate and ammonium bicarbonate directly reduced radial growth of
the fungus in vitro at 0.06-0.2 M, and that no lesions developed on
H. soZani-inoculated tubers treated with 0.2 M solutions of each of the salts
during 6 weeks of incubation at 22-24°C. Postharvest applications of these
compounds (at 0.2 M) on naturally infected field-grown tubers also
significantly reduced disease severity and Helminthosporium sporulation
after 15 weeks of storage at 10°C. In this case, radial growth inhibition of
H, solani on salt-amended media was generally predictive of the capability
of the salts to suppress lesion development and sporulation on potato
tubers. Similarly to the effect of the salts on P. digitatum, the citrus
pathogen (Smilanick et al., 1999), treatments with sodium and potassium
carbonate were also more effective than those with the respective
bicarbonate salts against H, solani growth (Olivier et al., 1998).
Several studies with carbonate and bicarbonate salts have confirmed
that the anions are primarily responsible for pathogen suppression by
inorganic salts, while the cations play only a minor role. However,
ammonium bicarbonate is an exception since, in addition to the anion,
ammonium too may contribute to the toxicity of the salt (DePasquale and
Montville, 1990).
Chlorine (as hs^ochlorous acid) is an effective and economical biocide
that has long been accepted as a potent disinfectant for sanitation
purposes and is recognized as safe in many countries (Eckert and Ogawa,
1988). Chlorination of the washing water used in tanks and hydrocoolers,
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