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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Biological Control Til
decay in lemons effectively if applied 24 h after inoculation, while the
antagonistic bacterium Pseudomonas cepacia was effective only if applied
within 12 h after inoculation (Smilanick and Denis-Arrue, 1992). The
antagonistic yeast Debaryomyces hansenii was effective against wound
pathogens in citrus fruits if applied 3 h after the fruit was inoculated
with the pathogen, but was ineffective 7 h after inoculation (Chalutz and
Wilson, 1990).
The time of application of the antagonist was found to be an important
factor in the control of Lasiodiplodia theobromae in banana fruits by
Trichoderma viride and other Trichoderma spp.: the highest reduction in
the infection rate was achieved when the antagonistic fungus was
applied 4 h prior to inoculation with the pathogen. There was less
disease reduction following simultaneous application, and the least
disease inhibition occurred when the Trichoderma was applied 4 h after
inoculation (Mortuza and Ilag, 1999). These results demonstrated that
the antagonistic Trichoderma species were not effective against
infections already established in the fruits and indicated that the nature
of the biocontrol activity is protective.
Another factor affecting the effectiveness of the antagonist is the
presence of moisture in the wound. The biocontrol of Botrytis cinerea on
apples was more effective when the antagonistic yeast Candida oleophila
was applied to fresh wounds rather than to 1-day-old wounds (Mercier
and Wilson, 1995). Introducing C. oleophila to wounds in apple fruit prior
to inoculation with B. cinerea significantly reduced the percentage of
gray mold of the fruit after 14 days at 18°C. However, as the fruit surface
dries, moisture rapidly becomes a limiting factor for yeast growth,
therefore, the application of the antagonist should follow the occurrence
of wounding as closely as possible (Mercier and Wilson, 1995). It is likely
that the poorer establishment of C. oleophila on dry wounds prevented it
from multiplsdng to population levels that would be inhibitory to
B. cinerea, although a dry environment could also interfere with the
mode of antagonistic action.
Zehavi et al. (2000) inoculated berries with B, cinerea, Aspergillus
niger and Rhizopus stolonifer in order to study the activity of epiphytic
microorganisms isolated from table and wine grapes, against these
pathogens. They concluded that wound inoculation is ideal for initial
screening of antagonists but that this situation differs from that in the
field. On the other hand, dipping grape bunches in an antagonist
suspension and then sprasdng them with the pathogen spore suspension
provides a closer simulation of a field biological control system, where the
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