Brassinosteroids Can Improve Juice Quality and Fruit Yield

Josh McGill Tip of the Week

By Fernando Alferez and Divya Aryal

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 that this treatment can become economically feasible.

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers are working to determine how Br treatment influences internal maturity in Hamlin and Valencia sweet orange varieties during fruit maturation. The goal is to find the ideal maturation stage for applying the hormone and to obtain the best sugar-to-acid ratio.

Brassinosteroids applied in March had a greater effect on Valencia yield than a January application.

Research results for the first season show that in Hamlin, Br application improved internal fruit quality by increasing sugar/acid ratio in juice from 9 to 12 by early December. A higher fructose content was also found in juice from Br-treated fruit. Brs induce accumulation of certain sugars in the juice. The brassinosteroid was applied by foliar spray in late November, and growers saw the effect in January.

In Valencia fruit, by harvesting in March, Brix in controls was 8.5, whereas in Br-treated fruit it was 9.4. An increase in Valencia yield, between 9% and 29% depending on the time of application, was also found after Br treatment. The best timing to achieve maximum results appears to be closer to harvesting, but this needs to be confirmed.

Acknowledgment: This project was supported with funding from the Citrus Research and Development Foundation.

Fernando Alferez ( is an assistant professor, and Divya Aryal is a research graduate assistant, both at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.

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