Fruit load restricts the flowering promotion effect of paclobutrazol in alternate bearing Citrus spp

► Paclobutrazol (PBZ) increases flowering in alternate bearing citrus trees. ► There is a cultivar-dependent crop load threshold value above which PBZ is unable to promote flowering. ► PBZ cannot promote flowering of heavy crop load trees regardless treatment date, dose applied or method of treatmen...

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Bibliographic Details
Published in:Scientia horticulturae 2013-02, Vol.151, p.122-127
Main Authors: Martínez-Fuentes, A., Mesejo, C., Muñoz-Fambuena, N., Reig, C., González-Mas, M.C., Iglesias, D.J., Primo-Millo, E., Agustí, M.
Format: Article
Language:English
Subjects:
Alternate bearing
buds
canopy
Citrus
clementines
Flowering
Fruit
fruit trees
fruits
inflorescences
oranges
Paclobutrazol
shoots
soil treatment
spraying
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Summary:► Paclobutrazol (PBZ) increases flowering in alternate bearing citrus trees. ► There is a cultivar-dependent crop load threshold value above which PBZ is unable to promote flowering. ► PBZ cannot promote flowering of heavy crop load trees regardless treatment date, dose applied or method of treatment. The floral bud inductive period, PBZ promotes flowering in Citrus; however, our results indicate that this effect is fruit-load dependant. In ‘Salustiana’ and ‘Navelina’ sweet oranges, ‘Hernandina’ Clementine mandarin, and ‘Afourer’ and ‘Moncada’ hybrids, flowering intensity significantly increased the following spring for medium-to-low fruit-load trees treated with either 1–10g PBZ tree−1 applied to the soil or 15g tree−1 sprayed on the canopy. PBZ significantly increased the percentage of sprouted buds and leafless floral shoots (both single-flowered shoots and inflorescences) and reduced the number of vegetative shoots. By contrast, heavy fruit load trees receiving the same amount of PBZ in the same season or at floral bud differentiation period scarcely flowered. Fruit nullified the effect of PBZ irrespective to treatment date (inductive period or bud burst) as well as the dose applied (1, 10 or 15g tree−1) or the treatment method (soil application or canopy spraying). In conclusion, the effectiveness of PBZ in promoting flowering in Citrus depends on the fruit load since the tree showed a cultivar-dependant threshold value above which PBZ is unable to promote flowering.
ISSN:0304-4238
1879-1018
DOI:10.1016/j.scienta.2012.12.014