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

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FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE Postharvest Disease Summary 317 by wet weather (Hewitt, 1974). The lesion is dark brown and firm and the margins of the infected area are less distinct than those of Cladosporium rot (Harvey and Pentzer, 1960). D. Aspergillus niger v. Tieghem This pathogen can be a serious problem when grapes are marketed at ambient temperatures (Mandal and Dasgupta, 1983). The fungus survives on plant debris in the soil at high temperatures (25-30°C) and airborne spores infect berries via injuries caused by insect punctures, splits and stem-end fractures. Infection occurs only in mature berries; young berries are resistant to infection even when wounded (Abdelal et al., 1980). Infection can also take place through injuries incurred during handling. Since the fungus does not grow at temperatures below 5°C, cold storage is effective in suppressing disease development (Matthee et al., 1975). E. Penicillium spp. Several species of Penicillium, including P. citrinum Thom, P. cyclopium West, and P. expansum Link, can infect harvested grapes causing the blue mold rot (Barkai-Golan, 1974). Although infection can sometimes be initiated before harvest, the disease is usually associated with wounds and cracks in the skin at harvest (Harvey and Pentzer, 1960). Infection is induced in injured berries by conidia, which are dispersed by air currents, winds and insects. Decay continues to develop, although at a very slow rate, during the prolonged cold storage of grapes at 0°C (Harvey and Pentzer, 1960), and it may spread through the bunch. F. Rhizopus stolonifer (Ehrenb. Ex Fr.) Lind and R. oryzae Went & Prinsen Geerligs Rhizopus rot, incited by both of these species, can become a problem for grapes that are marketed at ambient temperatures (Mandal and Dasgupta, 1983). The fungi exist and sporulate in the soil and on plant debris. Asexual spores (sporangiospores) are spread by air currents and primary infection is via injuries (Barbetti, 1980). R, oryzae is also capable of penetrating the intact skin of mature berries in the presence of exuded grape juice. Infection continues to spread during storage, when rotted berries infect adjacent healthy berries by contact. The infected tissue rapidly becomes covered with sporangia (white when young, later turning black), which are borne on sporangiophores that arise in clusters on the white mycelium. http://arab2000.forumpro.fr
FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE 318 Postharvest Diseases of Fruits and Vegetables Both species have high optimal growth temperatures (30-35°C for R. oryzae and 20-25°C for K stolonifer) and their development can thus be suppressed, similarly to that of A, niger, by refrigeration. Growth is resumed, however, on transfer of the fruits to shelf-life conditions. Control Measures Minimizing the amount of debris in the vineyard by sanitation measures, and injury prevention by gentle handling of the berries are important for reducing postharvest diseases initiated by wound pathogens. Thinning of bunches may also result in reduced cracking and splitting (Barbetti, 1980). Cold storage after rapid removal of the field heat is the basic means for decay suppression in grapes, while keeping them in a cool room throughout marketing will suppress decay at the end of the marketing chain (Beattie and Dahlenburg, 1989). The classic fungicidal means for decay control is periodical fumigation of the fruit with sulfur dioxide gas (Eckert and Ogawa, 1988), but this treatment may result in damage to the berries and in deposition of sulfite residues on their surface (Marois et al., 1986). Looking for alternatives to SO2, Forney et al. (1991) found that vapor-phase hydrogen peroxide suppressed germination of B. cinerea conidia on grapes and reduced the incidence of decay in non-inoculated fruits, without affecting their color or soluble solids contents. Fumigation of grapes with low concentrations of acetic acid was suggested by Sholberg et al. (1996) as a suitable alternative to SO2 for controlling decay in cold storage. At 0.27% (vol/vol), acetic acid-treated grapes did not show any phytoxicity and there were no differences between SO2 and acetic acid treatments regarding fruit color and composition. In addition to table grapes, wine grapes could also benefit from fumigation with acetic acid. Acetaldehyde vapors have also been considered as a possible treatment for controlling postharvest decay in grapes (Avissar and Pessis, 1991). However, acetic acid was found to be much more inhibitory to B. cinerea spores than acetaldehyde, and the latter has been reported to have some adverse effects on fruit quality, such as damage to the berries and an off-flavor in Thompson Seedless grapes (Pesis and Frenkel, 1989). KIWIFRUIT Several fungi are responsible for storage decay of kiwifruit. They include Botrytis cinerea, Penicillium spp., Phomopsis actinidiae, http://arab2000.forumpro.fr
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Post harvest diseases fruits and vegetables - Xavier University ...

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