Effects of Combined Treatment with Gibberellin and Prohydrojasmon on Volatile and Dimethyl Sulfide Content in Juice Sacs of Satsuma Mandarin (Citrus unshiu Marc.) Fruit During Maturation

Abstract

Combined treatment with gibberellin (GA) and prohydrojasmon (PDJ) is effective at reducing peel puffing in satsuma mandarin (Citrus unshiu Marc.). However, the effect of this treatment on volatiles remains unknown. In satsuma mandarin, dimethyl sulfide (DMS) is a key flavor compound. In this study, the effects of combined treatment with GA and PDJ on the content of volatiles, DMS, and S-methylmethionine (SMM), a precursor of DMS, in the juice sacs of satsuma mandarin were investigated. Mixtures of GA (1, 3.3, or 5 mg·L−1) and PDJ (25 or 50 mg·L−1) were applied to ‘Okitsu-wase’ and ‘Aoshima’ in mid-September. Gas chromatography-mass spectrometry analysis showed that among the volatiles, DMS content was reduced by the treatment, and was below the DMS odor threshold in several treatments. In ‘Okitsu-wase’, the DMS content in treated fruit was 1/3 to 1/17 of the control. In the treatment with GA and 50 mg·L−1 PDJ, a reduction in DMS content was observed until mid-November, irrespective of GA concentration, whereas in the treatment with 1 mg·L−1 GA and 25 mg·L−1 PDJ, the reduction was observed only until early November. In ‘Aoshima’, the DMS content was also reduced by the treatments, but in the treatment with 1 mg·L−1 GA and 50 mg·L−1 PDJ, the reduction was observed only until mid-November. Although the applied treatments delayed color development by approximately 1–2 weeks, this delay was not related to a reduction in DMS content. The effects on SMM and methionine content were small or negligible. As DMS has a strong odor, with trace amounts affecting fruit flavor, controlling DMS content is important. This study revealed that combined treatment with GA and PDJ reduced the accumulation of DMS in the juice sacs of satsuma mandarin fruits.