The aim of the research was to determine selected biochemical and physical characteristics and yielding of fruits in apple varieties (Malus domestica Borkh) such as Gala Schniga, Beni Shogun (Fuji) and Ligol, M.9 rootstock growing in the Wielkopolska region, Poland. high-performance liquid chromatography (HPLC) analysis revealed differences both in the profile and contents of soluble sugars and other metabolites detected in fruits of the tested apple varieties. The highest total saccharide content was found in fruits of cv. Gala Schniga, while leaves and shoots of this variety showed the lowest contents. Electron paramagnetic resonance (EPR) spectroscopy revealed the lowest contents of semiquinone radicals in apple fruits and the highest in leaves of apple trees. All organs of Schniga Gala apple trees were characterized by the highest levels of these radicals. Besides, gas chromatography-mass spectrometry (GC-MS) analysis of abscisic acid (ABA) revealed the highest levels of this molecule in shoots of apple trees, especially the Beni Shogun variety, while in fruits the levels were the lowest. Ligol fruits had the highest content of ABA. The percentage of injury observed after a low-temperature treatment and estimated on the basis of electrolyte leakage, was shown to be the lowest in fruits of the Beni Shogun variety. In turn, the lowest average yield of apple fruits was recorded for the Ligol and Fuji varieties, with the highest in the case of the Gala Schniga variety. At the same time, a significant variability in the average weight of fruits was observed; the highest average mass of fruits was recorded for the Ligol variety, while it was lowest for Gala Schniga. Additionally, firmness evaluation of the fruits revealed that the firmest fruits were harvested from Gala apple trees, before the Beni Shogun and Ligol varieties. A significant variability was recorded in the red blush on fruit surfaces of the tested varieties, with Ligol fruits having the weakest blush. Altogether, these results indicate that fruits of the analyzed apple varieties differed both in terms of their biochemical composition and physical characteristics.

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In Yesan-gun, Korea's main apple-producing region, the area of apple cultivation and yield are declining. In particular, the worsening quality of fruits due to unusually high temperatures amid recent climate change has also become a major challenge for apple orchards located on flatlands. The objective of this research is to investigate quality changes of apples according to different growing environments, depending on the shade of the sun, by covering the trees with different colors of wind nets. A white and blue wind nets with a hole size of 2 × 2 mm is installed on two experimental trees, 17-year-old 'Fuji' and 'Hongro', which are planted 1.5 m × 3.5 m in the north-south direction. Treatment of wind nets effectively lowered fruit surface temperature regardless of apple variety. When measuring the temperature of the fruit surface at 2 pm, the temperature of the air was 34.8°C, but the 'Fuji' of the untreated blocks was the highest at 40.0°C, while the blue wind net and the white wind net were significantly lower at 34.9°C and 36.6°C, respectively. In 'Hongro', the results showed that the surface temperature was effectively lowered by recording 38.3°C for the blue wind net and 38.5°C for the white wind net treatment when the untreated one was 44.2°C. According to the color difference in 'Fuji', the skin redness (a*) was the lowest with untreated control at 16.5, but the blue and white wind net treatment higher at 18.0 and 19.3, respectively. In 'Hongro', the white wind net treated fruit also showed a much higher skin redness than the untreated control of 28.1, showing much higher a* of 34.9. Sunburn damage in 'Fuji' apples amounted to 9.4% in untreated control. However, the blue and white wind net treatment revealed to 3.8% and 4.2%, respectively. In 'Hongro', those damage in the fruits treated with blue or white wind net, accounted for only 8.8% and 12.4%, respectively, significantly lower than 28.8% occurrence of untreated one. And, these results were understood to be the result of low UV radiation being blocked by the treatment of wind nets.

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