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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Biological Control 249
biological control of storage decay. Janisiewicz et al. (1991) demonstrated
that as the storage temperature of apples and pears decreased, there was
a reduction in the concentration of pyrrolnitrin (a metabolite of
Pseudomonas cepacia and other Pseudomonas spp.) needed to protect the
fruit from gray mold (Botrytis cinerea) and blue mold {Penicillium
expansum).
An integrated strategy to control postharvest decay in pome and stone
fruits has been advanced in recent years (Sugar et al., 1994; Spotts et al.,
1998; Willett et al., 1992); it comprises several pre- and postharvest
components (Sugar et al., 1994):
(1) Alteration of fruit nutrient status. This was found to influence the
susceptibility of pome fruits to decay, and includes calcium applications,
either as sprays during the growing season (Sugar et al., 1991) or by
pressure infiltration into the fruit (Conway and Sams, 1983), which
increase fruit calcium content and reduce the severity of decay. Lower
fruit nitrogen content has also been associated with reduced disease
severity. Management of pear trees for low fruit nitrogen (influenced by
timing of fertilizer application) combined with calcium chloride sprays
was found to reduce decay severity more than low nitrogen alone (Sugar
et al., 1992).
(2) Maturity at harvest. The severity of several postharvest diseases of
pears was found to increase as the fruit approached maturity or as
harvest was delayed, within the range of harvested maturity (Spotts,
1985).
(3) Controlled atmosphere storage. Atmospheres with reduced O2 and
elevated CO2 can reduce the severity of postharvest fungal decay in pome
fruits by inhibiting fruit senescence (Chen et al., 1981), thereby
maintaining host resistance to infection (Barkai-Golan, 1990).
(4) Application of low level of fungicide. All the components of the
integrated program were found to be compatible with thiabendazole,
which is used for postharvest decay control in pears (Roberts, 1991). This
is relevant when the combined treatment is aimed at controlling the blue
mold (P. expansum) in harvested pears. Thiabendazole is not effective
against Phialophora malorum, the causal agent of side rot of pears
(Willett et al., 1992).
Several yeast species, such as Cryptococcus laurentii, are capable of
colonizing wounds of pear fruit under conditions of low temperature
(0°C), ambient or reduced O2, and ambient or elevated CO2 (Roberts,
1991) and can, therefore, integrate into postharvest strategies. The
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