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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Biological Control 225
controlled atmospheres are applied for prolonged storage for other crops
as well, Arul (1994) pointed out the importance of testing the
effectiveness of antagonists under the intended storage conditions rather
than at ambient temperatures or in air.
The need for biocontrol agents with resistance to the chemicals
commonly used in fruit and vegetable production has been emphasized
by Spotts and Sanderson (1994). This feature is important since
biocontrol agents applied postharvest would contact residues of
fungicides which had been applied within a few days before harvest or
those applied postharvest to control decay.
While selecting antagonistic isolates, Sobiczewski et al. (1996)
emphasized microorganisms that are capable of inhibiting several
postharvest pathogens of the host. By screening of the antagonistic
effects of 107 isolates of epiphytic bacteria originating from apple leaves,
they found that only six of them satisfied this need and were capable of
inhibiting both B. cinerea and P. expansum, the two main postharvest
apple pathogens.
In a recent study, Schena et al. (1999) found that isolates of the
common yeast-like fungus, Aureobasidium pullulans at high
concentrations (10^ and 10'^ cells ml-i), were able to control Penicillium
digitatum on grapefruit, B, cinerea, R. stolonifer and Aspergillus niger on
table grapes, and B, cinerea and K stolonifer on cherry tomatoes. Less
decay control was exhibited at lower concentrations. The ability of
A. pullulans isolates markedly to suppress postharvest decay caused by a
range of pathogens on various fruits, and its ability to survive and
increase its population under a variety of field conditions and during cold
storage, suggested that this widespread and well adapted saprophytic
fungus be considered as a biocontrol agent against postharvest pathogens
(Leibinger et al., 1997; Schena et al., 1999). It is interesting to note that
some of the A pullulans isolates significantly reduced decay caused by
four different postharvest pathogens that could not be controlled with a
single chemical fungicide. Furthermore, the resistance of A. pullulans to
some commonly used fungicides (Lima et al., 1997) suggested the
possible integrated use of this antagonist with chemical fungicides, to
control postharvest rots.
However, A. pullulans is characterized by extreme morphological and
cultural variability and genetic instability (Bulat and Mironenko, 1992),
whereas genetic stability has been mentioned as an important feature
required for a successful biocontrol agent by Wilson and Wisniewski
(1989). Schena et al. (1999) have recently confirmed the high genetic
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