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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Means for Maintaining Host Resistance 141
GAs on fungal and bacterial growth in vitro has been recorded, and its
effect on the development of pathogens has been attributed to
maintaining the decay resistance of the fresh celery heads.
Dipping harvested celery heads in GA3 solution with TBZ and chlorine
served for many years in Israel as a standard treatment in celery
intended for export. A recent study showed that spraying the fields with
GA3 before harvest delayed the natural decrease in the antifungal
compound marmesin (Afek et al., 1995a). Maintenance of the high level
of marmesin in the petiole tissues after harvest was suggested to be the
mode of action by which the plant hormones inhibit decay development in
stored celery.
Delay of deterioration by the synthetic auxin, h-naphthalene acetic
acid (NAA) was studied in eggplants (Temkin-Gorodeiski et al., 1993).
Eggplant fruits deteriorate during prolonged storage, mainly because of
accelerated senescence of the calyx, which precedes deterioration of the
fruit. Dipping the calyx in NAA solution (200 ppm) maintained calyx
freshness, which is an important aspect of the appearance of the fruit,
but it did not prevent decay development. The addition of the fungicide
prochloraz (900 ppm) retarded both calyx senescence and decay
development, caused mainly by A. alternata, and kept the fruit firm.
Dipping the whole fruit gave even better results and the residual level of
prochloraz in such fruits was less than 0.34 mg T^, which is lower than
the maximal level approved by the authorities in Europe. A triple
combination of NAA, fungicide solution (Prochloraz, 900 mg l-i active
ingredient) and bulk packaging in polyethylene-lined bags with
water-absorbent materials, prevented water condensation and
maintained eggplant quality along with reduced incidence of decayed
fruit during storage (Fallik et al., 1994b). The higher levels of CO2
obtained within the bags (1.2%) may have partially contributed indirectly
to the inhibition of decay development, by delaying fruit senescence. Such
a combination could considerably expand the export potential of
high-quality fruit (Fallik et al., 1994b).
The use of auxins is limited since, in high concentrations, these
compounds might accelerate ethylene production and thus enhance the
aging process. In general, plant growth regulators may be of special
importance mainly for fruits and vegetables that cannot be stored at low
temperatures because of their cold sensitivity, as well as in developing
countries where cold storage cannot be applied.
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