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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
16 Postharvest Diseases of Fruits and Vegetables
A correlation between preformed antifungal compounds and resistance
to postharvest disease in the young fruit is found in various hostpathogen
systems. The presence of phenolic compounds in the young
banana fruits was reported as early as 90 years ago (Cook and
Taubenhaus, 1911); particular significance was attributed to the tannins
since they are often found in higher concentrations in unripe than in ripe
fruits. Examples of such antifungal compounds are the phenolic compounds
in apples, which inhibit pathogen development in the young fruit
(Ndubizu, 1976) and the 3,4-dihydroxybenzaldehyde compound that has
proven fungistatic activity in the green banana fruit (Mulvena et al., 1969).
Another example of a preformed compound is the glycoalkaloid
tomatine. Its presence at high concentrations in the young fruit peel has
been related to the quiescent infection of 5. cinerea in the green tomato
fruit (Verhoeff and Liem, 1975). In this case, however, the fungus would
not actively grow as the fruit ripened when the tomatine level
significantly decreases.
In unripe avocado fruit, a link was established between the presence of
a diene and of monoene antifungal compounds in the fruit rind and the
quiescent infection of C. gloeosporioides in such a fruit (Prusky et al.,
1982). The diene, which is the major compound, inhibits spore
germination and the growth of Colletotrichum mycelium in
concentrations lower than those present in the young fruit rind (Fig. 4).
2000 6000 10000 14000 18000
Antifungal diene concentration(j.ig/mr^)
Fig. 4. Effect of the purified antifungal diene from avocado peel on conidial
germination and germ tube elongation on Colletotrichum gloeosporioides.
(Reproduced from Prusky et al., 1982 with permission of the American
Phytopathological Society).
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