EFFECT OF ABA TREATMENT ON TANNIN ACCUMULATION AT AN EARLY STAGE OF FRUIT DEVELOPMENT IN PERSIMMON

Persimmon fruit accumulates large quantities of tannins and has astringent taste. However, there is a mutation type, in which the fruit stops tannin accumulation at early stages of development and loses astringency naturally on the tree. This mutation is called pollination constant and non-astringent (PCNA), since the fruit of this type can lose astringency despite not having seeds. Persimmon tannins belong to condensed tannins (CTs) and consist of proanthocyanidin (PA). PA biosynthesis in persimmon fruit is regulated by transcription factor DkMyb4, isolated from persimmon fruit, and the expression of this gene may be regulated by endogenous ABA as well as VvMyb during skin coloration in grape. We examined the effect of ABA on PA accumulation in PCNA persimmon fruit. Miyobi, a new fertilizer containing S-ABA (natural-type ABA), was used for the treatment at 400 mg/L equivalent of ABA and applied to the fruits of PCNA ‘Jiro’ and ‘Okugosho’. The treatment was applied at three-day intervals from one week after full bloom (WAFB) to 12 WAFB, and PA content was determined until the end of the treatment. ABA content of the treated and control fruit was also estimated by gas chromatography-mass spectrometry (GC-MS). The fruit of ‘Okugosho’ had a slight delay of PA decline following ABA treatment, but there was no effect in ‘Jiro’. The ABA content was higher in ‘Okugosho’ than in ‘Jiro’ at three WAFB, corresponding to PA concentration. However, we could not determine a relationship between ABA and PA content after 7 DAFB. Therefore, ABA may have an effect on PA accumulation of persimmon fruit depending on the cultivar or the absorbed amounts in the fruit at a specific stage.