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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Chemical Control 179
conidial germination but resulted in extensive stem browning and fruit
phytoxicity, which increased with the aldehyde concentration. The degree
of inhibition decreased with increasing aldehyde molecular weight. The
incidence of P. expansum decay was significantly impacted by aldehyde
identity and concentration and by the interaction of the two factors.
Since stem quality of sweet cherries is a critical component in the
evaluation of fresh fruit quality, the browning which follows aldehyde
treatments will limit their commercial use. On the other hand, stem
quality is less of a concern for fruits intended for processing, and for this
purpose aldehyde fumigation may present an alternative to the use of
synthetic fungicides.
Injuries resulting from acetaldehyde vapors have been reported for
various products, such as cultivars of apples (Stadelbacher and Prasad,
1974), strawberries (Prasad and Stadelbacher, 1974), grapes (Pesis and
Frenkel, 1989), lettuce (Stewart et al., 1980) and carrot tissue cultures
(Perata and Alpi, 1991).
Nine out of 16 volatile compounds occurring naturally in peach and
plum fruits greatly inhibited spore germination of B. cinerea and
Monilinia fructicola (Wilson et al., 1987a). The volatiles most effective in
inhibiting spore germination were benzaldehyde, benzyl alcohol,
y-caprolactone and y-valerolactone. Of these, benzaldehyde was active
at the lowest concentrations tested and completely inhibited germination
of B, cinerea spores at concentrations of 25 |il l^ and germination of M
fructicola spores at 125 |il l^. It was clearly shown that the same
compounds were effective on both fungi and that the relative inhibition
by these compounds was similar against each pathogen. Various volatiles
(benzaldehyde, methyl salicylate and ethyl benzoate) have been
recorded as growth suppressors. It is of interest to note that while
benzaldehyde and methyl salicylate were fungicidal against both
pathogens, another volatile, ethyl benzoate was fungicidal against one
pathogen (Monilinia) and fungistatic against the other pathogen
(Botrytis). The most effective volatiles were found to be active at
concentrations that should make them potential fumigants for
postharvest disease control (Wilson et al., 1987a).
Evaluation of 15 volatile odor compounds, released from raspberries
and strawberries during ripening, for their ability to inhibit postharvest
decay fungi, showed that five of them inhibited the growth of Alternaria
alternata, B, cinerea and Colletotrichum gloeosporioides directly on the
fruit at 0.4 [il ml-i (Vaughn et al., 1993). Among the five compounds,
benzaldehyde was the most toxic to the fungi and completely inhibited
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