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

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Attack Mechanisms of the Pathogen 63
A, alternata, Ozcelik et al. (1990) found that concentrations as high as
120.6mg of alternariol and 63.7mg of alternariol methyl ether per lOOg
tissue were recorded in inoculated tomatoes after 4 weeks at 15°C. The
highest in-tissue concentration of altenuene (19mg/100g) was found after
3 weeks at 25^C. However, tenuazonic acid was not detected in
inoculated tomatoes, regardless of the storage temperature or type of
packaging. Inoculations of Red Delicious apples indicated that alternariol
was also the predominant toxin in this fruit, although its in-tissue
concentrations were lower than those produced in tomatoes (e.g.,
49.8mg/100g at 25°C); relatively low concentrations were recorded for the
other two toxins, while tenuazonic acid was not detected in infected
apples (Ozcelik et al., 1990). Alternariol, alternariol methyl ether and
tenuazonic acid were recorded in A. alternata-infected peppers (Bottalico
et al., 1989).
In addition to their phytotoxic effects, non-specific toxins may also
function as mycotoxins - toxic to both humans and animals - as
antibiotic substances, as plant growth regulators, etc. Examples of
mycotoxins that also function as phytotoxins (Scheffer, 1983) are:
aflatoxins, produced by Aspergillus flavus and related fungi; citrinin,
patulin and penicillic acid, which are produced mainly by species of
Penicillium and Aspergillus; moniliformin and fumonisins produced by
strains of Fusarium moniliforme; and trichothecenes produced by various
fungi, such as species of Fusarium, Cephalosporium, Myrothecium,
Trichoderma and Stachybotrys. In addition to their mycotoxic effects on
humans and animals and their toxic effects on plants and plant organs,
the trichothecenes may also have insecticidal, antifungal, antibacterial,
antiviral, and antileukemic effects (Macko, 1983).
Of special interest to postharvest pathology is the production of
patulin by Penicillium expansum in pome and stone fruits. The amount
of patulin produced by P, expansum may vary greatly according to the
strain involved. Sommer et al. (1974) found that patulin production by
different strains of P. expansum in Golden Delicious apples ranged from
2 to 100 |xg/per gram of tissue. On the other hand, various apple and pear
cultivars may differ in their sensitivity to the same fungal strains. The
storage temperature is another factor affecting patulin production in a
given fruit cultivar. Paster et al. (1995) demonstrated that while more
patulin was produced in Starking apples than in Spadona pears held at
0-17°C, higher toxin levels were produced in pears than in apples held at
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