Brassinosteroids and Fruit Quality and Yield
Posted August 2025
Researchers: Fernando Alferez, Divya Aryal
Contact: Fernando Alferez, UF/IFAS SWFREC alferez@ufl.edu
Summary:
There are some indications that brassinosteroids (Brs) may advance commercial internal maturity by almost one month in ‘Valencia’ sweet orange, depending on the time of application. However, the best time of application in this variety and other sweet orange varieties like ‘Hamlin’, still needs to be determined, so this treatment can become economically feasible. We are working to determine how Brs treatment influences internal maturity in ‘Hamlin’ and ‘Valencia’ sweet orange varieties during fruit maturation, with the aim of finding the ideal maturation stage for applying the hormone and obtaining the best sugar-to-acid ratio. Our results for the first two seasons show that in ‘Hamlin’, Br application increased the sugar/acid ratio from 9 to 12 by early December on average. We also found a higher fructose content in juice from Brs-treated fruit. In ‘Valencia’ fruit, by harvesting in March, °Brix was increased by almost one degree unit. We also found that the health status of the tree determines the efficacy of Brs treatment. This means that the better health the tree shows, the better effect we get from the treatment. This past season we started treating with Brs trees that had been previously treated with oxytetracycline (OTC) injections. Our results this season confirm that in OTC-treated trees showing canopy recovery and better aspect, Brs may improve internal quality further, not only in terms of °Brix and ratio, but also in pound solids. Next season we will repeat treatments to confirm this result.
Take Home Message:
- Brs improve internal fruit quality by increasing the sugar/acid ratio in juice when applied close to harvesting.
- Brs induce the accumulation of certain sugars in the juice.
- Brs treatment is more effective in improving juice quality if trees were previously treated with OTC.
