ABSCISSION STUDY DURING CITRUS FRUIT MATURATION IN CORSICA: UNFAVORABLE ENVIRONMENTAL CONDITIONS FOR FRUIT SHEDDING

Citrus fruit development and ripening are complex processes involving physiological and biochemical changes that are under hormonal, nutritional and environmental control. One of the most evident phenomena in late maturation is shedding of ripe fruit. A study made in Spain on sweet oranges showed that fruit shedding was related to the increase of sugars content of fruit pulp juice. To investigate this potential relationship between fruit abscission and internal maturity parameters we investigated the fruit maturity process of 10 clementine × mandarin hybrids and 9 commercial sweet orange varieties with different maturity period. Morphological and biochemical analyses (acidity, total soluble solids, fruit weight thickness of the flavedo, thickness of the peduncle, external colo) were carried out on fruit sets of the different varieties during the maturation process, from December to June. The abscission initiation was evaluated by measuring the force required to detach the fruit of the peduncle. Analysis showed that under the local conditions, abscission was generally not expressed even through fruit maturation was evolving. Therefore, we suppose that even though the local conditions have an important effect, abscission of citrus fruit results also from environmental-genotype interactions. Moreover, evolution of abscission and fruit parameters are not correlated suggesting the independence in the process of maturation and abscission under the environmental conditions of Corsica.