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Grapes are used worldwide and are rich in polyphenols, such as anthocyanins and stilbene compounds. Wild grapes contain abundant stilbene compounds, which are beneficial to humans. This study examined the polyphenol content and gene expression involved in skin coloration in the ripening stage of Ampelopsis spp. Accession compared to ‘VC-1’ (Vitis coignetiae) and ‘Super Hamburg’ (V. labruscana). The flavonoid content was generally higher in the Ampelopsis fruit than in the other grape lines, and the highest content among Ampelopsis accessions was found in ‘YG10075’ at 9.67 mg quercetin equivalent (QE) per g fresh weight. The anthocyanin content was highest in ‘VC-1’ at 1.2% (w/w), and the Ampelopsis accession with the highest anthocyanin content was ‘YG10062’ with 0.27%. The resveratrol content was highest in ‘VC-1’ at 70.4 μg/g, and the Ampelopsis accession with the highest resveratrol content was ‘YG10075’ with 48.5 μg/g. Expression levels of genes involved in skin color development increased during maturation in ‘VC-1’ and ‘Super Hamburg’, but decreased with maturation in Ampelopsis ‘YG10042’, ‘YG10075’, and ‘YG10062’. The expression of the genes related to stilbene compound synthesis, skin coloration, and reactive oxygen species (ROS) was high in the leaves of ‘YG10045’, young berries of ‘YG10075’, and ripe berries ‘YG-Songni4’. The gene expression showed different patterns depending on the accession of Ampelopsis, the organ, and the ripening stage. Our results indicate that ‘YG-Songni4’ is the most valuable Ampelopsis spp. accession with the highest expression of genes related to synthesis of stilbenic compounds throughout all organs. This accession could be a useful genetic resource in grape breeding programs.

Due to recent abnormal weather caused by global warming, peach flowering has gradually accelerated, and spring frost damage caused by premature de-acclimation has increased. In this study, under a simulated spring frost environment using a Soil–Fruit–Daylit–System (SFDS) chamber, we investigated whether treatment with 2% cellulose nanocrystals (CNCs) could enhance the freezing tolerance of the flower buds from 2-year-old whole peach trees. Visual changes in the ice propagation were observed using an infrared camera at the same time. After the peach flower buds in the calyx red stage were placed in the SFDS chamber with a minimum temperature of −4 °C for ~20 h, the percentage of browning in the pistils and stamens was 57.0% in the control group and 14.1% in the group treated with 2% CNCs. During the first pink stage, the percentages of browning in the pistils and stamens in the control group and the group treated with 2% CNCs were 98.2% and 70.3%, respectively. However, when peach flower buds in the group treated with 2% CNCs were exposed to a −6 °C-targeted chamber, they could not mitigate frost injury. Almost all flower buds were damaged. Infrared thermal images showed that the first exotherm in the control group began at 2:33:03 am, whereas that of the group treated with 2% CNCs began at 3:01:33 am. The control started to express exothermic behavior at −4.2 °C, while the group treated with 2% CNCs started expressing exothermic behavior at −5.1 °C. Thus, treatment with 2% CNCs enhanced the freezing tolerance by −0.9 °C and delayed the first instance of exothermic behavior by ~28 min. These results indicate that treatment with 2% CNCs could mitigate the frost damage of peach flower buds in a frost environment of −5 °C.

Accumulated nutrient reserves provide an important energy source for deciduous fruit trees in their initial growth and development the following spring. This study investigated the effect of mid-season defoliation on the growth and accumulation of carbohydrate reserves of kiwifruit vines in Korea. The ‘Goldrush’ (Actinidia chinensis) vine was used for this experiment, following de-blossoming in spring. The vines were artificially defoliated to varying degrees at 1 month intervals from Jul. 15 to Oct. 14. The degree of defoliation was 0 (control), 25, 50, 75, and 100%. From Jul. 15 to Sep. 15, the dry weight of kiwifruit vines with 50% or more defoliation was reduced as compared to the control. In particular, 75 and 100% defoliation on Aug. 16 resulted in decrease of 79.2 and 83.1 g from the control vines (145.6 g), respectively. Defoliation on Aug. 16 decreased both the aboveground and underground dry weight of the vines. Most carbohydrate reserve of the young vines (which did not have fruit) accumulated in the roots. Defoliation on Aug. 16 and Sep. 15 reduced the accumulation of carbohydrate reserves, which was correlated with a decline in vine dry weight. For vines with 75% or more defoliation on Aug. 16 and Sep. 15, about less than half amount of starch accumulated in the roots as compared to the control (4.3 g per vine). In contrast, the accumulation of soluble sugars was not significantly influenced by defoliation, except for vines with 75% or more defoliation on Aug. 16. In conclusion, 75% or more defoliation on Aug. 16 and Sep. 15 has a negative impact on the growth and carbohydrate reserve of a new cultivar, ‘Goldrush’.

The effects of global warming and CO2 level were investigated on tree growth and fruit characteristics of ‘Niitaka’ pear. The treatments consisted of ambient temperature and 390 μL·L−1 CO2 (control group), ambient temperature + 4°C and 390 μL·L−1 CO2 (elevated temperature group), ambient temperature and 700 μL·L−1 CO2 (elevated CO2 group), and ambient temperature + 4°C and 700 μL·L−1 CO2 (elevated climate group). Fruit weight was the highest in elevated CO2 group (543.0 g), but lowest in elevated temperature group (394.3 g). Flesh firmness at harvest was the highest in elevated temperature group. For fruit skin color, Hunter L* and b* values were not significantly different among treatments, while Hunter a* value was higher on those treated with higher temperature and CO2 concentration. Photosynthetic rate in July and August was high in plants under elevated CO2 concentration. In contrast, the elevated temperature and elevated climate groups showed relatively high photosynthetic rate in early July, then became far lower than those of the control and the elevated CO2 group in late August. Rapid increase in fruit diameter was observed on fruits grown under elevated climate, then slowed down after the middle fruit growth stage. Soluble solids content increased at harvest time in groups with elevated CO2.

The lateral buds of non-branching chrysanthemum cultivars are affected by temperature and exogenous plant growth regulator (PGR) treatment. The number of axillary buds, endogenous indole-3-acetic acid (IAA) and t-zeatin riboside (t-ZR) concentrations by planting date and PGR treatments were investigated in three genotypes. Two non-branching genotypes, ‘Iwanohakusen’ and ‘01B1-8’ and branching type ‘Jinba’ were planted on May 2 and June 29. ‘Jinba’ always bore axillary buds and ‘01B1-8’ showed stronger non-branching traits than ‘Iwanohakusen’. Only 22.9% viable buds developed in the axils of ‘01B1-8’ whereas 68.7% developed in ‘Iwanohakusen’ on the May 2 planting date group. When planting was delayed from May 2 to June 29, the number of axillary buds decreased in both non-branching genotypes. Endogenous IAA concentrations remained unchanged and t-ZR concentrations decreased in all the three genotypes when the planting date was delayed. This reduced t-ZR level corresponds to the increased ratio of IAA/t-ZR. The number of viable axillary buds increased from 21.7% to 50.1% upon ethephon treatment and to 30.3% by synthetic cytokinin 6-benzylaminopurine (BAP) treatment in ‘01B1-8’. Viable axillary buds of ‘01B1-22’ increased from 17.1% to 25.1% and 29.1% respectively. Ethephon and BAP application decreased endogenous IAA contents and increased t-ZR contents. Elevated concentrations of t-ZR rather than IAA probably account for axillary bud formation in non-branching chrysanthemum. Just as the non-branching genotypes, the branching type cultivar ‘Jinba’ showed similar changes in IAA and t-ZR contents according to planting date and exogenous PGR treatments. These results showed that genotypic difference of branching patterns is not a result of concentration-dependent reaction.