Ultrastructural development and other characteristics of stylar-end russeting of 'navel' oranges in Florida

L. Gene Albrigo, Dianne S. Achor, Ken Townsend

Abstract


Stylar-end russeting (SER) of 'Navel' oranges often occurs in Indian River (IR) groves but is seldom seen in Central Ridge locations in Florida. Examination of the fruit peel in the summer revealed that the epidermal cell layer was ruptured, often in parallel arrays of cracks, in the stylar-end area. At this early stage of damage, there was no evidence of fungal involvement. By harvest, the injured area had a network of cracks. In the Ridge, the amount of SER was much greater in greenhouse conditions than when similar trees were outdoors. All cultivars of 'Navel' oranges examined in Indian River groves had some SER and year to year incidence was variable. Growth regulators applied during fruit growth did not affect the amount of SER, but Temik treatments in one year did reduce SER, while in the following year there was no affect of Temik on SER. Higher humidity in IR groves may favor fruit enlargement and thinner cuticles. Growth stress fracturing in relation to secondary fruit development as a mechanism for the cuticleepidermal rupturing is discussed.

Keywords


citrus sinensis; scanning electron microscopy; stylar-end russeting; 'Navel' oranges; peel disorders; temik

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283