ISHS Acta Horticulturae 1042: XII International Symposium on Plant Bioregulators in Fruit Production
FOLIAR 2,4-DICHLOROPHENOXY ACETIC ACID (2,4-D) APPLICATION AFTER PHYSIOLOGICAL FRUIT DROP REDUCES FRUIT SPLITTING AND INCREASES FRUIT SIZE IN MANDARIN |
| Authors: | O.P.J. Stander, K.I. Theron, P.J.R. Cronje |
| Keywords: | Citrus reticulate, rind quality, synthetic auxin, potassium, calcium |
| DOI: | 10.17660/ActaHortic.2014.1042.4 |
| Abstract:
Fruit size and the integrity of the rind are key components that determine the value of a citrus fruit. Fruit splitting is a physiological disorder caused by pressure resulting from the expanding pulp of an individual fruit on its rind, leading to cracks at the stylar-end of the fruit and eventual splitting of the fruit. The evaluation of 2,4-dichlorophenoxy acetic acid (2,4-D) to reduce splitting, was conducted on two different split-susceptible mandarin (Citrus reticulate) cultivars ‘Marisol Clementine’ and ‘Orri’. Treatments were applied as foliar sprays and commenced after physiological fruit drop (December), alone and in combination with Bonus-NPK. In January (±34 mm fruit diameter) and February (±42 mm fruit diameter) 10 mg/L 2,4-D were applied on its own. Application of 2,4-D directly after physiological fruit drop, either alone or in a tank-mix with K, consistently reduced the number of split fruit, and increased the growth rate (mm/day) of all the mandarin cultivars. Except for a slight increase in rind coarseness and reduction of juice content of treated fruit, internal and external fruit quality parameters were not significantly affected. The reduction of split fruit and enhancement of fruit growth could be explained by a possible enhancing effect on the growth of the rind’s cells, hence increased rind coarseness. A medium cover foliar spray of 10 mg/L 2,4-D directly after physiological fruit drop could be used for ‘Marisol Clementine’ and ‘Orri’ mandarin orchards with a history of severe fruit splitting. | |
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