Maturation curves and degree-days accumulation for fruits of 'Folha Murcha' orange trees

By N. M. C. Stenzel, C. S. V. J. Neves, C. J. Marur, M. Scholz, J. Gomes. 2006

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The effect of thermal summation on orange fruit growth on different rootstocks has not been studied for the State of Parana, Brazil. This research evaluated the growth of fruits by means of maturation curves, and quantified the growing degree-days (GDD) accumulation required for fruit maturation in 'Folha Murcha' orange trees budded on 'Rangpur' lime, 'Volkamer' lemon, 'Sunki' mandarin, and 'Cleopatra' mandarin, in Paranavai and Londrina, PR. In both locations and all rootstocks, the fruits showed evolution in total soluble solids (TSS) content in relation to GDD accumulation, with a quadratic tendency of curve fitting; total titratable acidity (TTA) had an inverse quadratic fitting, and the (TSS/TTA) ratio showed a positive linear regression. Fruits in Paranavai presented a higher development rate towards maturity than those in Londrina, for all rootstocks. The advancing of the initial maturation stage of fruits in Paranavai in relation to those in Londrina occurred in the following descending order: 'Volkamer' lemon (92 days), 'Cleopatra' mandarin (81 days), 'Sunki' mandarin (79 days), 'Rangpur' lime (77 days). In Londrina, trees on 'Rangpur' lime and 'Volkamer' lemon were ready for harvest 8 and 15 days before those on the 'Cleopatra' and 'Sunki' mandarins, respectively. In Paranavai, the beginning of fruit maturation in trees on 'Volkamer' lemon occurred 15, 19, and 28 days earlier than on 'Rangpur' lime, 'Cleopatra' mandarin, and 'Sunki' mandarin, respectively. Considering 12.8oC as the lower base temperature, the thermal sum for fruit growth and maturation of 'Folha Murcha' orange ranged from 4,462 to 5,090 GDD.

Subfields: Plant Science

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