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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
276 Postharvest Diseases of Fruits and Vegetables
At high dosage rates they have also provided a protective barrier on the
fruit surface, that inhibits Penicillium sporulation on decasdng fruits
(Eckert and Ogawa, 1985). Imazahl, a systemic fungicide characterized
by a different mode of action from that of the benzimidazole compounds,
effectively controlled P, digitatum and P. italicum on citrus fruits, and its
control extended to isolates resistant to the benzimidazole compounds.
Both groups of fungicides, however, are ineffective against sour rot
caused by Geotrichum candidum (Eckert and Ogawa, 1985). Following
the evolution of Penicillium strains resistant to imazalil, as to other
previously effective fungicides, new strategies and new chemicals are
constantly being evaluated and developed. (See the chapter on Chemical
Means - Postharvest Chemical Treatment).
Eckert and Eaks (1989) emphasized that since only P. digitatum
biotypes resistant to the fungicides can sporulate on the treated fruit,
fungicide application creates an ideal situation for the buildup of
resistant types of P. digitatum, which would lead to poor decay control.
Curing citrus fruits (holding them at temperatures and humidities
conducive to wound healing) has long been reported as a non-chemical
method for controlling decay by wound pathogens (Hopkins and Loucks,
1948; Brown, G.E., 1973). Healing of wounds and control of postharvest
decay has also been achieved by combining individual wrapping of citrus
fruit in plastic film, which leads to the formation of a water-saturated
atmosphere within the wrap, with curing at 36°C for 3 days
(Ben-Yehsoshua et al., 1987). Stange and Eckert (1994) showed that
dipping lemons in a surfactant solution prior to curing gave better
control of the green mold than curing alone.
Much research has been conducted on the development of biological
control means as alternatives to chemical treatments, for controlling
postharvest decay (Wilson and Wisniewski, 1989; Brown, G.E. and
Chambers, 1996). Chalutz and Wilson (1990) and Droby et al. (1992)
found that yeast species of the genera Debaryomyces and Pichia are
capable of inhibiting wound pathogens because of their rapid
development in wounds in citrus fruit peel. Arras (1996) found that
Candida famata was one of the most active yeasts against P. digitatum
in wounded fruits, while Smilanick and Denis-Arrue (1992) and
Smilanick et al., (1996) demonstrated that strains of the bacterium
Pseudomonas syringae could reduce the incidence of postharvest rot by
occupying the wounds. Isolates of the common yeast-like fungus,
Aureobasidium pullulans were reported by Schena et al. (1999) to control
P. digitatum at high concentrations on grapefruit.
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