Characteristic of fruit development for optimal harvest date and postharvest storability in ‘Skinny Green’ baby kiwifruit

Actinidia arguta, known as sarunashi in Japan, is a vine tree native to east-Asia, including Japan, that produces small fruit rich in anthocyanins, catechins, vitamin C, chlorophyll, beta-carotene and other polyphenols. Our study revealed the inhibitory effect of the juice of A. arguta (arguta-juice) toward the mutagenicity of food-derived carcinogens and polycyclic aromatic hydrocarbons using the Ames test, and antioxidant activity of arguta-juice as determined using a free radical scavenging assay. The formation of DNA adducts in liver of mice fed 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) decreased significantly following administration of arguta-juice. The preventive effect of arguta-juice on the induction of inflammation of mouse ear by 12-O-tetradecanoylphorbol-13-acetate (TPA) was revealed. The anti-carcinogenic effect of a topically applied partially purified fraction of A. arguta was revealed on skin tumorigenesis in mice induced by treatment with 7,12-dimethylbenz(a)anthracene and TPA. In an effort to reveal the mechanisms for antimutagenicity of arguta-juice, effects on the enzymes that metabolize xenobiotics were examined. Combined effects comprising i) inhibition of the metabolic activation of mutagens with phase I enzymes, but ii) no prevention on the activity of phase II detoxification enzyme, UGT, were observed. We also investigated the characterization and partial purification of the antimutagenic components in A. arguta, which suggested that the components in A. arguta responsible for the antimutagenicity were water-soluble, heat-labile phenolic compounds. These results suggested that components in A. arguta are attractive candidates for potential use as chemopreventive agents.

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Inhibitory effect of Actinidia arguta on mutagenesis, inflammation and two-stage mouse skin tumorigenesis

Haploids are important for studying plant breeding and genome sequencing. Regeneration from in vitro anther culture under aseptic conditions has achieved success in many higher plants. This study focused on anther culture of hardy kiwifruit (Actinidia arguta Planch.) to obtain haploid or double haploid plants that originated from microspores. Using the anthers of hardy kiwifruit as the test materials, we report the relationship between the microspore development stage and the bud morphological characteristics, some factors influenced the callus induction and the differentiation of the adventitious buds. The results showed that microspore development correlated with the bud diameter and morphological characteristics during development. The microspore development stage, pretreatment at low temperature (4 °C), basic medium, plant growth regulators and genotype all affect hardy kiwifruit anther callus induction, and the type and concentration of plant growth regulators significantly affect the regeneration of adventitious buds. The ploidy of 119 regenerated plants was verified using flow cytometry. The results showed that the ploidy of the plantlets obtained from the vitro anther culture of hardy kiwifruit was complex, being 3.36% haploid, 56.3% tetraploid, 4.20% hexaploid, and 36.13% octoploid.

Haploid plant regeneration from hardy kiwifruit (Actinidia arguta Planch.) anther culture

Ploidy and phenotype variation of a natural Actnidia arguta population in the east of Daba Mountain located in a region of Shaanxi

The fruit characteristics of hardy kiwifruit (Actinidia arguta) in Japan were investigated at several growth stages. Fruit weight of A. arguta ‘Mitsuko’ increased showing a double sigmoid curve. After fruit set, starch accumulated gradually and reached maximum concentration 90 days after full bloom (DAFB). Along with the reduction of the starch, sugar contents increased. Sucrose was a major sugar component in mature fruit. At the early stage of fruit development, myo-inositol was predominant. Quinic acid was prevalent in the young fruit. The amount of quinic acid decreased once in mid-season, and then increased slightly again. Citric acid increased gradually with maturation. The amount of malic acid and soluble oxalic acid was little affected by fruit maturity. The concentration of ascorbic acid was relatively high at the early stage of fruit development. It decreased in mid-season and then remained constant. Among the 2 cultivars and 14 local collections, the fruit shape varied being obovate, oblate, ellipsoid, and clavate. The fresh weight of 16 collected fruits ranged from 3.6 to 25.1 g. Fruit skin was glabrous and the surface color varied from green to dark green. Flesh color was basically green or dark green. Soluble solids content (SSC) of juice ranged from 10.2 to 17.0%. Sugar content varied from 4.1 to 9.5 mg · 100 g−1 FW. Myo-inositol content ranged from 266.4 to 771.1 mg · 100 g−1 FW. Major organic acids were quinic, citric, and malic acid, and citric acid was predominant. Total acid content ranged from 1.4 to 2.1 mg · 100 g−1 FW. Total ascorbic acid content ranged from 22.8 to 222.1 mg · 100 g−1 FW. Protease activity in the juice was generally high and varied from 6.1 to 92.6 nmol ρNA released · min−1, among the cultivars and local collections.

Hirofumi Satoh

Papers

Ploidy variation of hardy kiwifruit (Actinidia arguta) resources and geographic distribution in Japan