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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Biological Control 223
of Corynebacterium, Erwinia, Pseudomonas, Staphylococcus, Vibrio and
Xanthomonas. Of these, B, subtilis was the most effective antagonist.
The search for antagonistic fungi against Colletotrichum musae, the
causal agent of anthracnose of banana, revealed that almost all the fungi
isolated from banana fruit surfaces had at least some antagonistic effect
against the pathogen. The greatest antagonistic activity was recorded for
Alternaria tenuissima and Acremonium strictum, that effectively
inhibited Colletotrichum growth, both in vitro and on banana fruits
(Ragazzi and Turco, 1997). Searching for bacteria antagonistic to Botrytis
cinerea, the main pathogen of strawberry fruits, Moline et al. (1999)
showed that most of the 52 bacterial isolates that were obtained from the
surface of 'organically grown' strawberry fruits had some ability to
inhibit the growth of the fungus. Eleven of these, which were found
capable of interfering with conidial germination or fungal growth in
vitro, were selected for additional screening tests on JB. cmerea-inoculated
strawberry fruit. These isolates were identified as strains of
Pseudomonas putida and Chryseobacterium indologenes. Three of the
best isolates (two Pseudomonas and one Chryseobacterium) were also
found to reduce the incidence of gray mold rot on fruits under field
conditions (Moline et al., 1999).
Wilson et al. (1993) developed a method for the isolation and screening
of yeast antagonists. The method is based on the application of washings
to fruit wounds, which are then challenged with the fungal spores;
following a few days of incubation, microorganisms are isolated from the
non-infected wounds. Under these conditions, the predominant
microorganisms on the culture medium were of yeast species. Tests for
antagonism were performed with pure cultures under in vivo conditions.
Lorito et al. (1993) attempted to isolate selective biocontrol agents by
utilizing media with purified polymers, such as chitin, in order to detect
chitinase activity exhibited by the antagonistic microorganisms. Isolation
based on chitinase activity of the antagonist offers some level of selection
for properties potentially important to fungal control, but effective
microorganisms which do not produce chitinases could be missed by the
screening process. Some level of selection could also be achieved by using
media made of pasteurized or autoclaved homogenates of the pathogens
(Valois et al., 1996). This method may select only the microorganisms
that can live on specific cellular content. A simple selection method for
isolating bacterial antagonists to B, cinerea, which is both a pre- and a
postharvest pathogen of strawberries, was recently developed by Moline
et al. (1999); it is based on the ability of selected antagonistic bacteria to
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