We investigated the effects of elevated temperatures on the photosynthetic characteristics and fruit quality of the ‘Mihong’ peach (Prunus persica) under high carbon dioxide concentrations based on climate change scenario RCP 8.5. We simulated three different temperature conditions (control; the average temperature in normal years in Jeonju city, C+3.4 °C, C+5.7 °C) and 700 μmol·mol⁻¹ CO₂ (expected in the mid-21st century). The average photosynthetic rates were 10.64, 10.21, and 8.18 μmol∙m⁻²∙s⁻¹ at C+3.4 °C, control, and C+5.7 °C, respectively. The chlorophyll content in the control and C+3.4 °C increased compared to that at the early stage of growth, but that of C+5.7 °C decreased rapidly. The fruit weight was the highest for C+3.4 °C (158.2 g), followed by C+5.7 °C (129.5 g) and the control (127.3 g). The shoot length increased at C+3.4 °C and C+5.7 °C when compared to the control, and there was no significant difference in the other growth characteristics. The carbohydrate content was the highest at C+3.4 °C, and the nitrogen content increased as the temperature increased. Moreover, the C/N ratio decreased as the temperature increased but there was no significant difference. The rate of floral bud differentiation decreased as temperature increased, and that of C+5.7 °C was the lowest due to the low C/N ratio, vegetative growth dominance, and early defoliation. Furthermore, the floral bud density was low in the C+5.7 °C treatment. These findings indicate that a temperature increase of 5.7 °C under 700 μmol·mol⁻¹ CO₂ conditions will negatively affect the physiological response and fruit quality of the early-maturing peach variety ‘Mihong,’ and yield is expected to decrease in the following year.

Recent meteorological variability in winter and spring complicates predicting and managing frost damage in apples and pears. This study investigated the relationship between frost injury during the flowering stages of apples (‘Hongro’ and ‘Fuji’) and pears (‘Wonwhang’ and ‘Niitaka’) and weather conditions across regions at varying altitudes. Orchards were categorized into coastal, inland, mid-mountainous, and mountainous regions, and flowering stages and frost injury were analyzed. The flowering period of apples, from the onset of blooming to full bloom, averaged approximately 15 days, which was about 3 to 5 times longer than that of pears. Furthermore, the total flowering duration of apples was 1.5 to 2.0 times longer than that of pears. Additionally, flowering exhibited a tendency to be delayed at higher altitudes. However, orchards situated in mid-mountainous regions experienced earlier flowering compared to those in other regions. Among the two apple cultivars, the average frost damage was more severe in central flowers than in lateral flowers and was relatively higher in ‘Fuji’ than in ‘Hongro’. In pears, frost damage was most prevalent in the first to fourth flowers within the inflorescence, with ‘Wonhwang’ exhibiting relatively greater susceptibility than ‘Niitaka’. Across different cultivation regions, severe frost damage was observed in orchards located in mid-mountainous areas for both fruit species and cultivars. The severity of frost damage followed the order mid-mountainous, mountainous, plain, and coastal regions. Minimum temperatures were lowest in mid-mountainous and mountainous regions, while daily temperature differences were largest in mid-mountainous regions. Meteorological analysis (1981 to 2022) revealed consistent trends, with an increase in daily temperature range in recent years. These findings highlight the vulnerability of mid-mountainous orchards due to flowering stages overlapping with coastal and plain regions, exposing them to lower temperatures and larger temperature differences. Further studies on temperature variability are essential to mitigate frost damage risks.

This study was conducted to analyze the correlations among cracking occurrence, growth, and the fruit characteristics in 'Jinok' compared to 'Campbell Early' grapes (Vitis labruscana). The flower cluster length and berries of the two cultivars tended to increase slowly after an initial rapid growth at 23 to 50 days after bud burst and at 7 to 28 days after full bloom, respectively. The cracking of 'Jinok' and 'Campbell Early' grapes occurred 49 and 56 days after full bloom respectively, and the same times coincided with the early stage of fruit maturation when the berry enlargement was moderate. There were fewer cracked berries per cluster in 'Jinok' (3.3%) than in 'Campbell Early' (8.3%) during the harvest period. There were no statistically significant differences in the shoot length or petiole diameter according to the presence or absence of cracking, and among the fruit characteristics, the cluster with cracked berries had a large number of berries and a thick cluster stalk diameter. As a result of analyzing the relationships among variables through correlation and principal component analyses, it was found that the number of berries (r = 0.780**, r = 0.735**), the berry density (r = 0.778**, r = 0.736**), the cluster width (r = 0.318*, r = 0.608**), and the cluster weight (r = 0.672**, r = 0.621**) were closely correlated with the occurrence of cracking in the two cultivars. Therefore, maintaining an appropriate berry set amount per cluster in consideration of the cluster size will be a cultivation measure that can reduce the occurrence of cracking.

This study was carried out to compare fruit quality outcomes according to berry set levels, and to analyze the relationships among epicuticular wax, skin cell development, texture characteristics, and cracking sensitivity due to contact with neighboring berries under a condition of excessive-berry set per cluster of 'Jinok' and 'Campbell Early' grapes. A berry thinning treatment of both cultivars reduced the numbers of berries per cluster to 45, 60, 75, and 90 at 20 days after full bloom. With regard to the fruit quality characteristics, the number of berries, the berry density, and the cluster weight all showed increases with higher berry set levels, but the 75 and 90 berry thinning levels showed lower soluble solid contents and higher acidity than the 45 and 60 berry treatments. Significant berry cracking occurred in the 75 and 90 berry treatments in both cultivars, though its occurrence was significantly lower in the 'Jinok' than the 'Campbell Early' grape. A 'platelet' shape of epicuticular wax was observed on the non-contact side of the berries, but the contact sides of neighboring berries were poorly developed. The epidermal cells (outer and sub-epidermal) of the contact sides of neighboring berries were pressed down by internal and external growth pressure more than they were in normal berries (non-contact), showing a long oval shape with a long length and width. On the contact sides of neighboring berries of the 'Jinok' and 'Campbell Early' grapes, berry hardness was reduced by 23.9% and 36.5%, respectively, compared to non-contact berries.