Phenolic metabolism and antioxidant activity during endodormancy of Kiwifruit buds

Abstract

Bud dormancy is an adaptability process in woody plants that enables them to survive in unfavorable conditions. In the present study, the phenols, antioxidant capacity, and activity of three enzymes were evaluated during endodormancy phases in two Hayward and Tomuri cultivars and two female and male Golden genotypes of kiwifruit buds. The buds were collected from ten-year-old own-rooted vines from the end of October 2015 until the end of January 2016 in the north of Iran. The results revealed that phenols, antioxidant capacity (RSA), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO) activities of buds significantly increased at the beginning of endodormancy and subsequently decreased at the end of the endodormancy. The POD activity increased in Hayward and Tomuri from the onset of endodormancy and continued for two weeks after the endodormancy release. The total phenol had a positive and significant correlation with RSA and PAL enzyme activity. Furthermore, higher antioxidant capacity and phenols in both male and female Golden genotypes were attributed to the higher PAL enzyme activity in both genotypes. This study proposes that the RSA%, PAL activity, and phenol concentration could be employed as a biomarker to indicate bud dormancy phases in kiwifruit.