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

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Postharvest Disease Summary 301
Stud)dng the force required to break the epidermis of several cultivars,
as a criterion for resistance to wound pathogens, Spotts et al. (1999)
found that the epidermis of Golden Delicious and Jonagold was more
easily broken than that of other cultivars, while the epidermal tissues of
Fuji and Granny Smith were the most resistant to puncture.
The resistance of apples of various cultivars to core rot infection,
initiated by the penetration of B. cinerea, P, expansum, Mucor piriformis
and other pathogens, via the sinus between the calyx and the core cavity
(Combrink et al., 1985; Spotts et al., 1988), was evaluated according to
the presence of open sinuses (Spotts et al., 1999). The highest percentage
of fruits with open sinuses (with a mean of 38%) was recorded for Fuji
fruits; Granny Smith and Braeburn had the fewest fruits with open
sinuses, averaging 1.0 and 0%, respectively. Various biochemical and
physiological factors may influence the resistance of the cortex tissue of
apple fruits to decay pathogens. These include the presence of
glycoprotein inhibitors of pectolytic enzymes of the pathogen (Brown,
A.E., 1984) and the accumulation of the phytoalexinic compound, benzoic
acid (Seng et al., 1985).
Control Measures
The choice of treatment for controlling postharvest diseases of pome
fruits depends, to a large extent, on the nature of the pathogens involved,
the source of infection and the time of infection (Edney, 1983; Eckert and
Ogawa, 1988). The lenticel rots are caused largely by pathogens present
in the orchard and this enables us to treat these infections by preharvest
orchard sprays. In areas suffering from heavy losses as a result of
lenticel rots, orchards are sprayed with fungicides in the late summer to
suppress the production of inoculum of Gloeosporium spp. and Nectria
galligena and to protect the fruit lenticels from quiescent infections
(Corke and Sneh, 1979; Edney, 1983). Corke and Sneh (1979) found that
the efficiency of preharvest systemic fungicides in reducing decay by
Gloeosporium perennans was related to their ability to suppress fungal
sporulation. After harvest, the fruits are treated with a systemic
fungicide to suppress the development of quiescent infections of
Gloeosporium in the lenticels. The control of the lenticel rotting is
considered to be one of the greatest contributions made by systemic
benzimidazole compounds following their introduction as postharvest
fungicides in the late 1960s. It is their ability to reach the lenticels,
which are located within the fruit peel, that enables these fungicides to
control rotting (Leroux et al., 1975). However, the penetration ability of
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