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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
274 Postharvest Diseases of Fruits and Vegetables
cultural conditions. The infection may remain latent in the form of
appressoria, in which case disease is manifested only during transport
and storage (Fisher, 1970; Brown, G.E., 1975). Anthracnose may invade
the fruits after harvest, in the packinghouse, in storage or in the market;
it gains entrance to the fruit via mechanical injuries or dead buttons.
Mature green fruits are sensitive to infection after prolonged exposure to
ethylene during the degreening, since this treatment renders the intact
peel easily penetrated by the pathogen. Affected fruits are characterized
by the development of sunken lesions that, under humid conditions, form
abundant salmon-pink masses of spores that later turn into brown-black
masses.
The incidence of anthracnose can be reduced by washing, which
removes the quiescent appressoria (Smoot and Melvin, 1971; Brown,
G.E., 1975), before degreening with ethylene. This, however, cannot be
done commercially because washing retards the degreening process.
Several factors affect the severity of anthracnose: (1) orange-colored
fruits are more resistant to the disease than pale or green-colored ones
(Brown, G.E. and Barmore, 1976); (2) degreening with ethylene at
concentrations higher than those required for optimal chlorophyll
degradation (5 |LI1 per liter of air) favors anthracnose development;
(3) fungicide application prior to degreening reduces anthracnose
development (Brown, G.E. and Barmore, 1976). Resistance to
anthracnose was induced in mature green tangerines treated with
ethylene after being washed to remove dormant appressoria (Brown, G.E.
and Barmore, 1977). Application of ethephon (a chemical which produces
ethylene on degradation) to Robinson tangerines 5-7 days before harvest
significantly reduced the incidence of anthracnose (Barmore and Brown,
G.E., 1978); control was attributed to the accumulation in the interior of
the fruit of ethylene which induced physiological changes leading to the
development of resistance.
5. Trichoderma viride Pers. ex S.F. Gray
This fungus, which is responsible for Trichoderma rot in storage, is
frequently considered to be a pathogen of minor importance. It can,
however, cause serious loss in some citrus-growing areas.
The fungus is known as a soil inhabitant and is capable of
decomposing cellulose. Germinating conidia enter through mechanical
injuries on the fruit, at the stem end or the stylar end (Gutter, 1961).
This fungus is often overgrown by other organisms, particularly by
Penicillium digitatum with which T. viride is often confused because of
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