Variation of Chemical Composition and Antioxidant Properties of Kiwiberry (Actinidia arguta) in a Three-Year Study.

The quality of fruit as a source of bioactive ingredients is related to the genetic characteristics of plants, but it can also be modified by growing conditions. Therefore, long-term research can be extremely valuable in evaluating various crop plants, especially novel ones. The aim of the research was to test four popular European kiwiberry (Actinidia arguta) cultivars ('Geneva', 'Bingo', 'Weiki', 'Anna') in terms of selected morphological features, yield, and chemical composition as well as their variability over 3 years. It can be concluded that the studied genotypes were very diverse in terms of the biochemical compounds' concentration in individual seasons. The cultivars 'Anna' and 'Weiki' were the most similar ones with respect to each other in terms of morphology and chemical composition. The cultivars 'Bingo' and 'Geneva' were definitely different. 'Bingo' was characterized by the largest and most uniform fruits in each season and had the highest concentration of vitamin C but the lowest carotenoid concentration. In turn, 'Geneva' produced the smallest fruit in each season with the highest concentration of polyphenols and a high concentration of carotenoids and displayed the highest antioxidant capacity regardless of the determination method. The research was performed with the application of computer-supported statistical analysis.

Apple Antioxidant Properties as an Effect of N Dose and Rate-Mycorrhization Involvement: A Long-Term Study.

The genetic and/or the agronomic approaches are two main ways to enhance concentrations of biologically active compounds in fruits and vegetables. In this study, the apple antioxidant status was evaluated from the second to the fourth year after planting in relation to an increasing N-dose applied-with or without plant microbial inoculation in the field conditions. Cultivar 'Sampion Arno' was selected to test these relationships. In the growing season, N treatment and inoculation effects were monitored for the apple peel total phenolics and selected individual phenolic compounds ((+)-catechin, (-)-epicatechin, chlorogenic and caffeic acids, rutin and phloridzin) and total ascorbate concentration. Additionally, as an environmental stress marker measurement of glutathione reductase, ascorbate peroxidase and catalase activity were conducted. The year effect was most pronounced, while the N or applied inoculum effects were much weaker. Great differences in antioxidative enzyme activity and phenolic concentrations between years were revealed. Nitrogen fertilization reduced the fruit's global phenolic accumulation compared to the control, but the N-effect varied depending on individual phenolic compounds, N dose and N application method. None of the tested factors influenced the ascorbate concentration. There was a certain tendency to increase antioxidant properties in the control group (without mineral N fertilization) but with the application of bio-fertilizer, which may seem promising for future research in this scope.

Growing Season, Cultivar, and Nitrogen Supply Affect Leaf and Fruit Micronutrient Status of Field-Grown Kiwiberry Vines.

The N uptake can affect kiwiberry yield and quality; however, the relationship between an increasing N dose and micronutrient accumulation in leaves and fruit is still to be elucidated. Interrelationships between essential nutrients are one of the most important issues in terms of effectiveness in plant mineral nutrition. A pattern in leaf nutrient accumulation throughout the growing period is required to indicate a suitable sampling time for the purpose of nutrient diagnostics and controlled plant feeding. The experiment was conducted on two commercially available cultivars of kiwiberry, 'Weiki' and 'Geneva', during the 2015-2016 growing seasons with an increasing soil N fertility (30-50-80 mg N kg-1 soil DW) to test the relationship between soil N level and leaf/fruit micronutrient concentration. The leaf Zn, Cu, Fe, and Mn concentrations significantly increased with a higher N supply in 'Geneva', while in 'Weiki' only Mn increased. Leaf B, Fe, and Mn gradually increased throughout the growing season, while Cu decreased. Between mid-July and the beginning of August, the lowest fluctuations in the micronutrient contents were recorded. The effect of the growing season on leaf micronutrient accumulation was highly significant; except for Fe, significantly higher micronutrient levels were revealed in 2016. Compared to the leaves, the growing season effect was smaller in the case of fruit micronutrient concentrations. Irrespective of cultivar, the increase in N fertilization resulted in a higher fruit Mn concentration and was insignificant in the case of other micronutrients. The results indicate that the N dose may affect the accumulation of micronutrients within a certain range depending on the tissue type and the genotype.

Actinidia arguta Leaf as a Donor of Potentially Healthful Bioactive Compounds: Implications of Cultivar, Time of Sampling and Soil N Level.

The aim of this study was to assess the enzymatic and non-enzymatic antioxidant status of kiwiberry (Actinidia arguta) leaf under different N regimes tested three times in field conditions during the 2015 growing season in two cultivars ('Weiki' and 'Geneva'). Leaf total antioxidant capacity using ABTS, DPPH and FRAP tests was evaluated in the years 2015 to 2017, which experienced different weather conditions. Both cultivars exhibited a significant fall in leaf L-ascorbic acid (L-AA) and reduced glutathione (GSH) as well as global content of these compounds during the growing season, while total phenolic contents slightly ('Weiki') or significantly ('Geneva') increased. There was a large fluctuation in antioxidative enzyme activity during the season. The correlation between individual antioxidants and trolox equivalent antioxidant capacity (TEAC) depended on the plant development phase. The study revealed two peaks of an increase in TEAC at the start and end of the growing season. Leaf L-AA, global phenolics, APX, CAT and TEAC depended on the N level, but thiol compounds were not affected. Over the three years, TEAC decreased as soil N fertility increased, and the strength of the N effect was year dependent. The relationship between leaf N content and ABTS and FRAP tests was highly negative. The antioxidant properties of kiwiberry leaves were found to be closely related to the plant development phase and affected by soil N fertility.

Bioactive compounds, total antioxidant capacity and yield of kiwiberry fruit under different nitrogen regimes in field conditions.

BACKGROUND: Actinidia arguta known as the 'kiwiberry' or 'mini kiwi' is relatively new among the cultivated berry species. Recent studies indicate the kiwiberry fruit could be an important source of many health-promoting compounds. A knowledge-based fertilisation concept was evolved to define optimal strategies for feeding Actinidia with nitrogen (N) because a deficit and excess of N both have a negative impact on plants and the surrounding environment. RESULTS: Kiwiberry yield and fruit internal quality significantly depended on soil N level, cultivar and growing season. A higher soil N led to an increase in carotenoid content and a decrease in phenolic content, whereas ascorbic acid and glutathione contents were not affected by soil N fertility. Under the highest N dose, enzymatic antioxidants were activated. Trolox equivalent antioxidant capacity clearly decreased with an increasing N level. CONCLUSIONS: Competent and skilful fertilisation management should focus on balancing a high fruit yield and maintaining their high quality. Based on yield level and fruit antioxidant potential, the N guide values for A. arguta vary between 30 and 50 mg N per kg-1 of soil. The recommended N dose may depend on overall soil quality traits and cultivar N demand, as well as on weather conditions. © 2020 Society of Chemical Industry.

Apple peel as a contributor to whole fruit quantity of potentially healthful bioactive compounds. Cultivar and year implication.

On the basis of the fresh weight of apple fruit and its peel and the concentration of bioactive compounds, the total quantity of L-cysteine, glutathione, ascorbate, flavonols, and anthocyanins as well as phenolics was evaluated in a wide range of cultivars and two growing seasons. Apple peel as a contributor to the entire apple quantity of the examined components considerably differed in relation to the investigated compounds and was also highly cultivar dependent. A great amount of flavonols was found in apple peel (approximately 40%), followed by ascorbate (approximately 30%) and total phenolics (approximately 20%), while the lowest contribution was assessed for thiols (approximately 11% and 14% for L-cysteine and total quantity of glutathione, respectively), based on average values for both years. Seasonal variations in the quantity of antioxidants was more pronounced in apple peel, whereas the contribution of apple peel to the whole fruit was predominantly affected by the genotype. A very high positive correlation existed between apple peel and the whole fruit quantity of antioxidants.

Relationship between apple peel and the whole fruit antioxidant content: year and cultivar variation.

Antioxidants are usually considered with regard to plant defense mechanisms due to the oxidative stress or their importance for human health or both. In the present research, a comprehensive study was made to test the relationship between the antioxidant content in apple peel and the whole fruit in two growing seasons. Antioxidants were mainly localized in the apple peel, but cultivars exhibited very high biodiversity in the distribution pattern. High or very high correlation coefficients between apple peel glutathione reductase and catalase activity as well as ascorbate, glutathione, and anthocyanins concentrations and the whole fruit were discovered on the basis of both fresh and dry weight basis in two growing seasons: 2004 and 2005. In the case of ascorbate peroxidase activity and phenolics or flavonol contents, it was proven only in 2005. It seems that apple peel could be a good marker of health values as well as antioxidant potential of apple fruit. Additional arguments, as compared to the previous study, were incorporated to support the suggestion of glutathione reductase as worth considering as an environmental stress marker and/or signalling molecule.

Great differences in antioxidant properties exist between 56 apple cultivars and vegetation seasons.

The contents of ascorbate, thiols, and phenolic compounds and antioxidative enzyme activity were measured in the apple peel of 56 genotypes after harvest in two vegetation seasons, 2003 and 2004. The main reason of great interest in these bioactive compounds is their well-established physiological role in all living systems. The biggest differences between tested genotypes were noted for ascorbate peroxidase and glutathione reductase (GR) activity, followed by total ascorbate, phenolics, and glutathione concentration; the least difference was observed in the case of catalase. A large cultivar variation was noted in the anthocyanins and flavonols contents. Distinguishing the cultivars with the lowest, highest, relatively stable or those in which antioxidant content greatly differed depending on growing seasons was attempted. The GR activity is proposed as an environmental stress marker of apple fruit.