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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
162 Postharvest Diseases of Fruits and Vegetables
strategy considerably decreased the incidence of P, expansum strains
resistant to TBZ during storage (Prusky et al., 1985a).
Following the development of benomyl-resistant strains of B. cinerea,
one of the most important pre- and postharvest pathogens of grapes,
Chiba and Northover (1988) studied the fungitoxicity of four synthesized
alkyl isocyanate homologues of benomyl towards both benomyl-resistant
and benomyl-sensitive isolates of the fungus. On the basis of spore
germination as a criterion for fungal response, the benomyl-resistant
isolates were found to be more sensitive than the benomyl-sensitive
isolates to ethyl isocyanate and propyl isocyanate. This response was
inverse to the relative response of sensitive and resistant isolates to
benomyl and constituted an example of 'negative cross resistance' (Chiba
and Northover, 1988). When the germ-tube length of Botrytis
germinating spores was used as a criterion, the four isocyanate
homologues of benomyl - methyl, ethyl, propyl and hexyl - were found to
be as effective against sensitive isolates as benomyl, but more effective
against the resistant isolates. The hexyl isocyanate homologue was less
effective than the other three compounds. Studies with wounded apples
clearly demonstrated that, while benomyl gave better protection against
sensitive isolates of JB. cinerea, the ethyl isocyanate homologue of benomyl
was effective against both benomyl-sensitive and benomyl-resistant
isolates.
Iprodione and vinclozolin, which are dicarboximide fungicides, have
been represented as alternative treatments to TBZ in many commodities,
such as cucumbers, tomatoes, strawberries, eggplants and grapes
(Lorenz, 1988). These fungicides are characterized by a different
mechanism of action from that of the benzimidazoles, although this
mechanism is not yet clear. Iprodione retards the development of
Botrytis, Penicillium, Monilinia and Rhizopus and it is, therefore,
capable of suppressing the main storage diseases of stone and pome
fruits (Bompeix and Morgat, 1977; Heaton, 1980). However, the
emergence of Penicillium expansum strains resistant to both iprodione
and vinclozolin, may prevent their use for decay control on these fruits
(Rosenberger and Meyer, 1981). In contrast to TBZ, iprodione is also
effective against Alternaria, and considerably reduces the incidence of
the black spots caused by this fungus on mangoes (Prusky et al., 1983)
and on potato tubers in Israel (Droby et al., 1984). However,
iprodione-tolerant isolates of Alternaria alternata pv. citri have already
been found in Mineola tangelo orchards in Israel and Florida, where the
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