Development of Technology to Reduce Rind Puffing in Satsuma Mandarin Fruits through Combined Treatment with Gibberellic Acid and Prohydrojasmon

Abstract

In recent years, increasing instances of rind puffing in satsuma mandarin fruits due to global warming have made long-term post-harvest storage difficult. Although the effect of gibberellic acid (GA) on rind puffing was previously clarified, treatment with low concentrations of GA has not been visibly effective in reducing rind puffing, and significant delays in color change have been observed following treatment with high concentrations of GA. In this study, we tested the effect of various spraying times and concentrations of GA mixed with prohydrojasmon (PDJ) on the delay in color change of satsuma mandarin fruits. A mixture of GA and PDJ at the same concentrations (3.3–20 ppm) inhibited rind of puffing; on the other hand, treatment with GA of 10 ppm or more sometimes led to a significant delay in coloring. Therefore, it was concluded that using a low concentration of GA (3–5 ppm) with a high concentration of PDJ (25–50 ppm) had a stabilizing effect on rind puffing with only a slight delay in color change. In the late-maturing cultivar ‘Aoshima unshu’, the effect of spraying this mixture in early September was highest in all treated periods. However, at the production site, there was a strong demand to suppress the delay in color change associated with GA treatment as much as possible. Upon re-examination of the effects of the concentrations and period of treatment, it was determined that treatment with a mixture of GA at 1 ppm and PDJ at 25 ppm could reduce rind puffing and suppress the delay in color change. It is now possible to use this mixture in early-maturing cultivars, and widespread use in satsuma mandarin production areas has been adopted. This technology has achieved the desired reduction in rind puffing and decay for short- and long-term storage of satsuma mandarin fruits, and will be indispensable for citrus cultivation in the future.