Postharvest Calyx Retention of Citrus Fruit

Abstract

Abscission is an active developmental process occurring at the abscission zone of the fruit peduncle. The target cells in the abscission zone, which are involved in the process of separation, are located in the separation layer, which is organized in a few cellular layers. In general, it is accepted that the increase in ethylene production in the fruit is followed by increased sensitivity of these cells to ethylene, which would lead to abscission. The abscission process is divided into two phases with respect to sensitivity to auxin and ethylene. The auxin, 2,4-D (2,4-dichlorophenoxy acetic acid), has been used as a postharvest packhouse treatment to retard calyx abscission (to repress postharvest decay). Commercially the sodium salt 2,4-D (Deccomone ® ) is applied to the fruit in a dip treatment at 500 ppm. The aim of this experiment was to test three agrochemicals (aminoethoxyvinylglycine (AVG), 1-naphthylacetic acid (NAA) and 1-methylcyclopropene (1-MCP)) that could possibly replace the postharvest application of the auxin 2,4-D. AVG had a fruit firming effect but no significant effect on calyx retention. NAA resulted in a high percentage of abscission, probably due to auxin overdose. The 1-MCP at low concentrations of 100 ppb and 250 ppb resulted in calyx retention but had a desiccating effect on the calyx whereas at a high concentration of 500 ppb there was a significant increase in calyx abscission. There was no loss of internal quality or colour. To conclude, according to what is known about the role of ethylene in abscission, 1-MCP and AVG should have prevented abscission of the calyx. Unfortunately, the results show that this complex plant mechanism is not so readily manipulated and 2,4-D remains the best product to inhibit calyx abscission of citrus fruit.

Mejora de la Tecnología de desverdización de cítricos y aptitud a la frigoconservación de nuevas variedades. Estudios sobre parámetros de calidad y composición nutricional.

“…HF-Calibra® treatments at different doses proved effective to reduce calyx alterations if compared with the controls, and the observed reduction was similar to or higher than that obtained by 2,4-D. The effectiveness of 2,4-D on control calyx abscission in degreened citrus fruit observed herein corroborates previously reported results (Jiménez-Cuesta et al, 1983;Cronjé at al., 2005;Carvalho et al, 2008;Martinez-Jávega et al, 2008b;Salvador et al, 2008). The obtained data showed a similar effectiveness of HF-Calibra® on reducing calyx senescence than 2,4-D treatment in all the assayed varieties.…”

“…As a postharvest treatment, the application of ethylene during degreening treatment can accelerate transpiration and drying, browning and abscission of the calyx (Cohen, 1978;Cronjé et al, 2005;Salvador et al, 2008). The susceptibility to these undesirable effects of ethylene is cultivar dependent (Carvalho et al, 2008).…”

“…In order to retard calyx senescence that occurs as a consequence of the degreening process, synthetic auxins like 2,4-dichlorophenoxy propionic acid (2,4-D) have been studied as a postharvest treatment to maintaining the final quality of the degreened fruit (Sonkar et al, 1999;Tatli and Ozguven, 1999;Cronjé et al, 2005).…”

“…It is widely known that the exogenous application of ethylene can also produce undesirable effects, such as accelerating calyx browning and abscission (Cronjé et al, 2005;Salvador et al, 2008), enhancing chilling injury symptoms (Yuen et al, 1995), inducing decay incidence (Smilanick et al, 2006) and increasing the development of off-flavors (Testoni et al, 1992).…”

“…Nevertheless, the postharvest application of ethylene during degreening not only causes the desirable color change in citrus fruit, but can also produce undesirable effects relating to accelerated fruit senescence such as drying, browning and abscission of the calyx (Cohen, 1978;Cronjé et al, 2005;Martínez-Jávega et al, 2008a;Salvador et al, 2008Salvador et al, , 2010. There have been reports that susceptibility to these undesirable effects of ethylene is cultivar-dependent (Carvalho et al, 2008;, although the incidence of these alterations is associated mainly with inappropriate degreening process conditions; the longer the exposure time, the more susceptible citrus fruits to senescence alterations becomes.…”