Rootstock Effects on Anthocyanin Accumulation and Associated Biosynthetic Gene Expression and Enzyme Activity during Fruit Development and Ripening of Blood Oranges

Zhaofang Chen,Youting Yang,Shengjia Huang,Zhihui Wang,Liping Tan,Sichen Li,Honghong Deng,Liancong Yang,Bo Xiong,Guochao Sun

doi:10.3390/agriculture12030342

Abstract

Blood orange (Citrus sinensis L. Osbeck) is a rare commercial citrus fruit containing abundant anthocyanins and has numerous health benefits. Blood orange rootstock determines the fruit yield and quality. This study evaluated the effect of the three most commonly used rootstocks on the fruit features, color index, physicochemical parameters, anthocyanin accumulation, the anthocyanin biosynthetic gene expression, and the associated enzymes during the fruit development and ripening of ‘Tarocco’ blood orange. The highest anthocyanin content at harvest was found in blood orange trees grafted onto ‘Trifoliate orange’ (Poncirus trifoliata L. Raf., Pt) rootstock. Molecular analyses revealed that the rootstock affects the anthocyanin accumulation in the blood orange. Additionally, there was a strong correlation between the anthocyanin content and the expression and the activity of related genes and enzymes, respectively. Based on gene expression and enzymatic activity analyses, Pt rootstock promotes a very high anthocyanin accumulation in ‘Tarocco’ blood orange fruit. Accordingly, Pt is the promising rootstock for producing good quality and highly nutritious ‘Tarocco’ blood orange fruit for commercial purposes.

Highlights

The epicarp gradually changed from green (July–October) to yellow-orange (November 2020–January 2021) and dark orange, and to slightly blush red tones (February–March) across the developmental stages (Figure 1A)
The color of fresh pulp changed from pale yellow (July–September) to yellow-orange (October 2020–January 2021) and red-orange (February–March 2021) (Figure 1B)
The General Features of the Fruits The fresh weight remarkably increased during the early expansion stages (90−180 days after full bloom (DAFB)), gradually increased during the veraison stages (210−270 DAFB), and remained nearly constant in the later stages as the fruit ripened (270−345 DAFB) (Figure 2A)

Summary

Introduction

Osbeck) originated centuries ago from a spontaneous genetic mutation of the common sweet orange [1]. The fruit is thought to have originated from China or the Mediterranean climate area [2], and its cultivation has since spread to other citrus-producing countries, such as Italy, Spain, the United States, Australia, and China. There has been a global increase in the demand and consumption of blood oranges, given their high anthocyanin concentration and abundant bioactive compounds [3]. The brilliant red coloration of blood orange is attributed to anthocyanins [4], which are not usually found in other citrus fruits [2]. Anthocyanins possess antioxidation, antiinflammatory, and anti-apoptotic properties. As such, it ameliorates oxidative stress, regulates inflammation, and prevents cancer, diabetes, cardiovascular, and neurological diseases [5]

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Discussion

Conclusion