EFFECT OF ETHYLENE SUPPRESSION ON HEPTOSE SUGARS METABOLISM AND RIPENING IN AVOCADO 'HASS' FRUIT

M.D. Meyer, L.A. Terry
The heptose (C7) sugar, mannoheptulose and its corresponding alcohol, perseitol, are the predominant non-structural carbohydrates in avocado (Persea Americana Mill.) fruit. Earlier work suggested that avocado fruit ripening could be associated with C7 sugars metabolism or that C7 sugars themselves may control the ripening process, acting as a ripening inhibitor(s). This work investigated the effects of delaying ethylene-induced ripening on C7 sugars content in avocado fruit. Early and late season avocado ‘Hass’ fruit originating from Spain and imported into the UK were treated with either 1-methylcyclopropene (1-MCP) or held in presence of a novel Palladium (Pd)-promoted ethylene scavenger (e+® Ethylene Remover). Fruit were stored at 5°C (late season fruit) or 5°C followed by shelf life ripening at 20°C (early season fruit). Fruit firmness and non-structural carbohydrates concentrations were monitored at defined intervals. Postharvest treatments significantly delayed softening vs. controls during storage at 5°C. Controls and fruit previously held in presence of the scavenger softened (<10 N) within 3 days shelf life whilst 1-MCP-treated fruit remained firmer. Substantial amounts of mannoheptulose and perseitol were found in early season fruit and showed a significant decline over storage time at 5°C. Moreover, 1-MCP and e+® Ethylene Remover -treated fruit, which had highest firmness value, also had greatest amount of mannoheptulose and perseitol, respectively. Further decline in C7 carbohydrates was observed as fruit ripened at 20°C. Fruit treated with 1-MCP had significantly more mannoheptulose vs. controls. Meanwhile, late season fruits were all characterized by quasi-absence of mannoheptulose, in spite of ripening being delayed in response to 1-MCP and e+® Ethylene Remover. The present study supports the hypothesis that avocado fruit has the ability to metabolize C7 sugars during ripening. However, since C7 carbohydrates concentrations were not systematically related to ripeness state, this suggests that C7 sugars may not be the only ripening mediator, such that other bioregulators (possibly modulated by the action of ethylene) could be involved in the control of ripening process.
Meyer, M.D. and Terry, L.A. (2010). EFFECT OF ETHYLENE SUPPRESSION ON HEPTOSE SUGARS METABOLISM AND RIPENING IN AVOCADO 'HASS' FRUIT . Acta Hortic. 884, 87-94
DOI: 10.17660/ActaHortic.2010.884.8
https://doi.org/10.17660/ActaHortic.2010.884.8
bioregulator, ethylene scavenger, mannoheptulose, 1-MCP, Persea Americana Mill., perseitol
English

Acta Horticulturae