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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
CHAPTER 11
BIOLOGICAL CONTROL
Increased official and public concern about the presence of fungicide
residues in foods, and the development by pathogens of resistance to
major fungicides, are two important reasons for the enhanced interest in
the possibility of using biological control as an alternative, non-chemical
means of decay suppression.
The term 'TDiological control" or ^iDiocontrol" refers to the use of
naturally found microorganisms which antagonize the postharvest
pathogens we wish to suppress. Antagonism between microorganisms is
a ubiquitous phenomenon involving fungi (including yeasts) and bacteria
which naturally inhabit the soil and the surfaces of various plant organs
(Blakeman and Fokkema, 1982; Fokkema and van den Heuvel, 1986;
Andrews, 1992). It is assumed that biocontrol of plant diseases occurs
naturally on aerial plant surfaces and may be one of the main reasons
why crops are protected to some extent during their cultivation (Droby et
al., 1996).
One of the approaches to the isolation of antagonistic microorganisms
for controlling postharvest diseases is through the promotion and
management of natural epiphytic antagonists, already present on fruit
and vegetable surfaces. Preharvest pesticide application and various
postharvest treatments, such as fungicide and wax sprays, washes and
dips, can greatly affect the resident microflora, both qualitatively and
quantitatively. It has been commonly observed that the common practice
of postharvest washing of harvested fruits and vegetables to obtain clean
produce, may affect the microbial populations by removal of naturally
occurring microorganisms. Fungicides may change the epiphytic
microflora by affecting microorganisms other than the pathogens against
which they are directed. These changes can, in turn, affect the pathogen
resistance of the host. Such practices could possibly be modified to
promote beneficial antagonistic microflora (Wilson and Wisniewski,
1989). To manipulate epiphytic microbial populations of fruits and
vegetables effectively, in order to control decay, information is needed on
their ecology. Spurr et al. (1991) suggested that emphasis be placed on
studying the impact of the environment on the microflora and that of
preharvest, harvest and postharvest activities on disease development.
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