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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Postharvest Diseases of Fruits and Vegetables
1x 2x
Relative concentration of orange volatiles
Fig. 3. Effect of concentration of the synthetic mixture of volatile compounds on
the germination of Penicillium digitatum spores. Ix is the concentration typical
of the natural mixture measured surrounding wounded oranges. Bars indicate
standard errors. (Reproduced from Eckert and Ratnayake,1994 with permission
of the American Phytopathological Society).
The fact that the average quantity of volatile compounds emanating
from wounded fruits was 75 times greater than that from non-injured
fruit may explain the lower germination of P. digitatum spores on water
agar exposed to sound citrus fruits. The terpenes alone, in several
concentrations and combinations, failed to stimulate spore germination
significantly above its level on water agar. On the other hand, a synthetic
mixture of limonene, the major terpene in the wounded fruit atmosphere,
with acetaldehyde, ethanol and CO2, at concentrations similar to those
measured in the atmosphere around wounded oranges, stimulated spore
germination on water agar to the same degree as the natural mixture of
volatiles.
It is interesting to note that volatile compounds evolved from diced
peels of various Citrus spp. (oranges, lemons, grapefruits, tangerines,
kumquats) have also induced stimulation of germination of P. digitatum
spores. Furthermore, lemons infected with Phytophthora citrophthora,
Geotrichum candidum or P. digitatum also emanated volatiles that
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