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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
140 Postharvest Diseases of Fruits and Vegetables
the climacteric respiration and maintains the level of climacteric
ethylene (Aharoni, 1994) (Fig. 25). Along with the delay in the senescence
process, there was a reduction in leaf decay during storage.
Experiments conducted in Israel with Romaine lettuce showed that a
single spray in the field with GA3 (25 ppm), several hours prior to
harvest, delayed deterioration during storage by delaying leaf yellowing.
In parallel, there was a reduction in the rate of decay caused mainly by
Sclerotinia sclerotiorum and soft rot bacteria (N. Aharoni and R.
Barkai-Golan, unpublished data).
The addition of GA3 (10 ppm) to a disinfecting solution containing
thiabenolazole (TBZ) and chlorine resulted in considerable delay in celery
senescence as expressed by the delayed yellowing of the petioles and
leaflets. Along with the maintenance of celery freshness, fungal soft rots
caused by S. sclerotiorum and Botrytis cinerea, and bacterial soft rot
caused by Erwinia carotovora were reduced (Barkai-Golan and Aharoni,
1980). It is interesting to note that the decrease in decay following GA3
treatment is greater than the decrease caused by the chemicals alone,
and that is manifested mainly in the prevention of decay progress along
the petiole during storage. TBZ itself exhibits activity similar to that of
the plant hormones, and it has a synergistic effect with GA3 in the delay
of senescence processes in celery leaves and petioles. No direct effect of
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GA3 concentration (ppm)
Chlorophyll _L i n
Respiration
Ethylene
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Fig. 25. Effect of GA3 concentrations applied to chives immediately before harvest,
on levels of chlorophyll, respiration (CO2 emanation) and ethylene production rates
after 7 days at 20°C in darkness (Reproduced from Aharoni, 1994).
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