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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
156 Postharvest Diseases of Fruits and Vegetables
effective against stem-end rot fungi, such as Diplodia and Phomopsis,
and does not protect the fruit against initiation of infection by either
Penicillium spp. or stem-end pathogens. Biphenyl is not active against
Geotrichum, Alternaria or Phytophthora (Eckert and Eaks, 1989).
Although biphenyl is still sometimes used in export shipments, mainly
by impregnation into paper sheets covering the fruit in the container, its
commercial utilization is discouraged by consumer resistance to the
characteristic odor of the treated fruit and by undesired residues on the
fruit.
Sodium or^/io-phenylphenate (SOPP) is an example of a broadspectrum
fungicide, effective against many postharvest pathogens. It is
used mostly against fungal pathogens but is also known for its
antibacterial properties. The undissociated phenol (or^/io-phenylphenol)
penetrates with comparative ease into the surfaces of various fruits and
vegetables, causing phytotoxicity and leaving considerable residues on
the fruit. However, a solution of SOPP containing excess alkali to
suppress hydrolysis of the salt, with a pH around 11.5, is both effective
and quite safe for treatment of several fresh fruits and vegetables. These
include citrus fruits, apples, pears, peaches, tomatoes, peppers,
cucumbers, carrots and sweet potatoes.
Although the intact cuticle of the fruit is not permeable to aqueous
solutions of the fungicide, the crop is generally rinsed lightly with fresh
water to remove most of the fungicide from the surface of the product,
leaving a significant residue at the injured site. The fungicide has,
therefore, a double function: (1) it eradicates fungal spores and bacteria
cells infesting the surface of the treated commodity; and (2) through
accumulation in the wound site, it prevents infection via wounds during
storage and marketing (Eckert, 1978).
The intensive and continuous use of biphenyl and SOPP has led to the
development of Penicillium digitatum and P. italicum strains resistant to
these chemicals (Dave et al., 1980; Eckert and Wild, 1983; Houck, 1977).
Furthermore, Penicillium isolates that are resistant to SOPP show
cross-resistance to biphenyl, which is structurally related to it.
Sec-butylamine (amino-butane) was developed as a postharvest
fungicide for citrus fruits in the mid 1960s (Eckert and Kolbezen, 1970).
It has a relatively narrow spectrum of antifungal activity and its main
function is the prevention of wound infection by Penicillium digitatum
and P. italicum; it does not, however, suppress their sporulation on
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