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Title: The effects of a surface coating on the development of post-harvest fungal rots of pome fruit with special reference to 'Conference' pears
Author: Bancroft, Roger David
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1990
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The impact of TAL Pro-long and certain other sucrose ester coatings on the development of six common post-harvest fungal rots of pome fruit was investigated. The preparations were not observed to be fungistatic but TAL Pro-long did diminish the incidence of fungal infections on conference pears held in cold storage. At higher temperatures, depending on the nature of the disease, the coatings were able to modify the spatial distribution and reduce the rate of spread of the lesions within apples (cvs 'Chiver's Delight', 'Cox's Orange Pippin' and 'Granny Smith's') and pears (predominantly cv. 'Conference'). In comparison to the rate of decay in non-coated fruit, TAL Pro-long had a greater effect on those rots caused by Botrytis cinerea Fr., Monilinia fructigena (Aberh. & Ruhl.) Honey and Rhizopus nigricans Lind. than those of Alternaria alternata Fr., M. laxa (Aberh. & Ruhl.) Honey and Penicillium expansum Link em. Thom. The efficacy of the treatments was attendant on the ability of the surface coatings to ameliorate the rate of fruit ripening and was much influenced by the composition and concentration of the preparations, the variety of the fruit, the timing of the applications (relative to the onset of ripening and the climacteric rise in ethylene), and the temperature to which the produce was subsequently exposed. Studies indicated that, in Conference pears, the profile of simple sugars and the activity of certain extracellular enzymes produced by M. fructigena and P. expansum were modified by TAL Pro-long. The changes in enzyme activity were not obviously correlated with the development of the rots but there was an apparent association between coating and the reduced availability of monosacharides and sucrose in the tissues of the host. The sucrose ester coatings accentuated the differential permeability of the fruit skin to gases leading to a rapid decline in oxygen and a rise in carbon dioxide. Experiments indicated that such modified gas environments were unlikely to prevent the growth of pathogens but that they did effect the production and action of ethylene. It is suggested that the internal gas atmospheres established within the fruit delayed the inactivation of hormonal 'senescence retardants' and thereby diminished the sensitivity of the tissues to ethylene with the result that the rate of ripening was reduced and the innate resistance mechanisms of the fruit were retained for an extended period.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available