POSSIBLE CAUSE OF ASTRINGENT PEACH FRUIT AND BIOSYNTHESIS OF PEHNOLIC COMPOUNDS

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 08456021
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 園芸・造園学
• Research Institution: OKAYAMA UNIVERSITY
• Principal Investigator: KUBOTA Naohiro OKAYAMA UNIV., FAC.AGR., PROFESSOR, 農学部, 教授 (70033272)
• Co-Investigator(Kenkyū-buntansha): FUKUDA Fumio OKAYAMA UNIV., FAC.AGR., ASISTANT, 農学部, 助手 (60294443)
• Project Period (FY): 1996 – 1998
• Keywords: Peach / Fruit / Astringency / Growing conditions / Phenolic content / Synthesis of phenolic compounds / PAL / Phenolic composition

Research Abstract

The total phenolic contents in the mature 'Hakuto' peach fruits varied widely among the orchards while significant difference among trees in the same orchard was not observed. Phenolic content ded not correlate with the contents of tatal solublee solids, fruit weight, and tree age. The larger the total phenolic contents, the higher was the EC of soil, but the relationship between total phenolic contents and soil pH was not observed.
Regardless of orchard, phenolic contents in fruit decreased towards the end of Stage 1 of fruit growth, after which it increased rapidly and reached a maximum in the middle of Stage 2. Phenolic contents rapidly decreased to a lower level during Stage 3. Throughout fruit growth, total phenolic contents were larger in the fruits from orchard which phenolic content in the mature fruits was high than in the fruits from orchard which it was low, especially during Stage 2. The relationships between phenolic contents and the shoot growth and soil moisture were not observed. PAL (L-phenylalanine ammonialyase) activity was high during Stage 1 and reached a maximum in the middle of Stage 2, after which no activity detected. Throughout Stage 1 and the first half of Stage 2, the larger the phenolic contents, the higher was the PAL activitiy in fruit. However, no relationship was observed between the PAL activity and the contents of N, Mn, Cu and B which have been related to phenolic metabolism.
Total phenolic contents in the mature fruits were the highest in Mishima-hakuto and Golden Peach, followed in Okubo and Hakuto, while it was very low in Kawanakashima-hakuto and nectalin. In almost cultivars, molecular weight of phenolics was large in Stage 1 and was low in Stage 2, after which it increased again during Stage 3. The HPLC analysis showed that six phenolic compounds were present in peach fruit irrespective of cultivar. Content of catechin was larger than in that of chlorogenic acid during Stage 1 and 2, while in stage 3 latter was larger than in the former.