Delay of early fruitlet abscission by branch girdling in citrus coincides with previous increases in carbohydrate and gibberellin concentrations |
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Authors: | Jalel Mahouachi Domingo J Iglesias Manuel Agustí Manuel Talon |
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Institution: | (1) Departamento de Suelosy Riegos, Instituto Canario de Investigaciones Agrarias, Apdo. 60, E-38200 La Laguna, Santa Cruz de Tenerife, Spain;(2) Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias, E-46113 Moncada, Valencia, Spain;(3) Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, E-46022 Valencia, Spain |
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Abstract: | Current evidence in citrus indicates that gibberellins (GAs) are main determinants of early fruit set while subsequent growth
of developing fruits is mostly dependent upon carbohydrate availability. In this work, branch girdling performed at anthesis
in Satsuma mandarin (Citrus unshiu (Mak.) Marc.) cv. Okitsu transitorily reduced early abscission rates (12–32 days after anthesis, DAA) delaying initially
the process of natural fruitlet drop. The effects of girdling on growth, gibberellin (GA) and carbohydrate concentrations
in developing ovaries and fruitlets were assessed during this initial growth stage (0–69 DAA). In girdled branches, abscission
rate reduction was preceded by elevated concentrations of carbohydrate and GA in developing ovaries and fruitlets. Girdling
at anthesis stimulated higher hexose (21 DAA) and starch (6–20 DAA) concentrations and also higher GA1 (6 DAA), GA19 (13–20 DAA) and GA20 (6–20 DAA). The results established a relationship between the reduction of early abscission rates and higher concentrations
of carbohydrates and GAs induced by girdling in developing fruitlets. These findings revealed that girdling certainly increased
GA concentration and strongly suggested that its effect on early fruitlet abscission delay is likely mediated by both GA and
carbohydrates. |
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Keywords: | Gibberellins Hexoses Okitsu satsuma Starch Sucrose |
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