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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
228 Postharvest Diseases of Fruits and Vegetables
fungi are sparse, most berries are not wounded and the antagonist,
applied as a spray, covers the fruit.
Reductions in the percentage of decay, or in its rate of development in
storage have been reported, following both field sprays with the
antagonistic organism suspension and a postharvest application.
Preharvest application
Since the infection of fruits by postharvest pathogens often occurs in
the field prior to harvest (see the chapter on Postharvest Disease
Initiation - Pathogen Penetration into the Host), it is no wonder that
preharvest application of the antagonist may sometimes be advantageous
in controlling postharvest diseases. For this approach, successful
biocontrol strains should be able to tolerate not only low nutrient
availability but also UV-B radiation and climatic changes (Schena et al.,
1999).
Field sprays of strawberry flowers with antagonistic non-pathogenic
Trichoderma isolates resulted in a decreased incidence of gray rot (B.
cinerea) during storage (Tronsmo and Dennis, 1977). Similarly,
application of epiphytic isolates of the yeast-like fungus Aureobasidium
pullulans, one of the most widespread saprophytes in the phylosphere, to
strawberries grown under plastic tunnels, markedly reduced storage
decay by both S. cinerea and R, stolonifer (Lima et al., 1997). The
antagonists were more effective when applied at the flowering stage than
at fruit maturity. Under these conditions, A. pullulans showed
significantly higher activity against Botrytis rot than the fungicide
vinclozolin.
An isolate of A. pullulans was found to reduce gray mold in table
grapes significantly when applied several times in the field, and its effect
was not significantly different from that of the chemical control
(iprodione) (Schena et al., 1999). It is worth noting that populations of
this antagonist rapidly increased on grape berries under field conditions,
and that they increased further during cold storage (0°C). Moreover, this
antagonist was able to survive and increase its population when
transferred to a new environment characterized by high temperature and
low relative humidity. Considering its high biocontrol efficacy and its
ability to survive and control gray mold in diverse environmental
conditions, this cosmopolitan yeast-like fungus was considered as a
potential biocontrol agent, especially where the use of chemical
protection is restricted (Schena et al., 1999).
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