Application of gibberellic acid and CPPU increases berry size and yield of highbush blueberry (Vaccinium corymbosum) 'Spartan'
We investigated the effects of applying plant growth regulators gibberellic acid (GA) and CPPU to whole plants of the highbush blueberry cultivar Spartan aiming to produce large-sized blue berries. Experiments were conducted from 2011 through 2017 in the experimental field of the Department of Agriculture at the Tokyo University of Agriculture, Japan. The effects of a single application of 100 mg L‑1 GA, 10 mg L‑1 CPPU, or a mixture of both growth regulators at the same concentrations were analyzed in 2011 and 2012. Each compound was sprayed on blueberry bushes 4 to 6 days after flowering. Results showed that GA, CPPU, and the GA-CPPU mixture all increased average berry weight, proportion of large berries, and total fruit yield, whereas no significant treatment effect on fruit set was detected. Berry maturity was delayed by a few days in the CPPU and GA-CPPU mixture-treated plants. In 2016 and 2017, we compared treatments consisting of 100 mg L‑1 GA spraying 5 days after flowering followed by 20 mg L‑1 CPPU spraying 10 days after flowering. This treatment combination increased average berry weight by 14 to 32% each year, respectively. Total berry yield was 1.0 to 1.3 kg bush‑1 higher (i.e., 3.8 kg bush‑1 in 2016 and 3.5 kg bush‑1 in 2017) than the yield of untreated plants. Meanwhile, berry maturity was delayed a few days by the treatment. Our results indicate that the application of these growth regulators was effective in enhancing the production of large berries and fruit yield of highbush blueberry Spartan.
Fujisawa, H., Kawai, Y. and Ishikawa, K. (2019). Application of gibberellic acid and CPPU increases berry size and yield of highbush blueberry (Vaccinium corymbosum) 'Spartan'. Acta Hortic. 1265, 85-90
GA, forchlorfenuron, fruit set, berry-size distribution, berry maturity