Dilraba Muhtar

Sweet cherry (Prunus avium L.) is a high-value horticultural crop; however, winter freezing injury significantly limits its introduction and stable production in cold-temperate regions. In this study, annual shoots of 16 major sweet cherry cultivars were collected during the dormancy phase and subjected to a simulated low-temperature gradient. Eight physiological indicators, namely, relative electrolyte conductivity (REC), malondialdehyde (MDA) content, osmoregulatory substances, and antioxidant enzyme activities, were systematically measured along with the poststress recovery growth percentage (RP). The semilethal temperature (LT₅₀) was calculated using a logistic equation, and a multidimensional comprehensive evaluation system for cold tolerance was constructed using the membership function method, principal component analysis (PCA), and cluster analysis. The results indicated that low-temperature stress significantly induced membrane lipid peroxidation and osmotic compensation in the shoots. PCA revealed four principal components—osmoregulation potential, cell membrane damage threshold, cold-protective protein synthesis, and membrane stability—with a cumulative variance contribution rate of 79.47%. Correlation analysis revealed no significant correlation between LT₅₀ (reflecting thermodynamic survival capacity) and the recovery growth percentage (reflecting poststress regenerative capacity), suggesting that “passive endurance” and “active recovery” in sweet cherries are two relatively independent physiological processes. The comprehensive evaluation model classified the 16 cultivars into four cold-tolerance tiers: High Tolerance (Russia 8, Reid, Pacific Red, and Brooks); Moderate-High Tolerance (Tieton, Jiahong, Sandra Rose, and Rivedel); Moderate-Low Tolerance (Luyu, Rocket, Tamara, Lapins, Frisco, and Taisho-nishiki); and Sensitive (Summit and Kordia). The four-dimensional evaluation model developed in this study provides a scientific basis for cultivar selection in cold regions and offers a theoretical reference for the trade-off of traits in future molecular breeding for cold resistance in cherries.

Sweet cherry (Prunus avium L.) is a high-value horticultural crop; however, winter freezing injury significantly limits its introduction and stable production in cold-temperate regions. In this study, annual shoots of 16 major sweet cherry cultivars were collected during the dormancy phase and subjected to a simulated low-temperature gradient. Eight physiological indicators, namely, relative electrolyte conductivity (REC), malondialdehyde (MDA) content, osmoregulatory substances, and antioxidant enzyme activities, were systematically measured along with the poststress recovery growth rate (RR). The semilethal temperature (LT₅₀) was calculated using a logistic equation, and a multidimensional comprehensive evaluation system for cold tolerance was constructed using the membership function method, principal component analysis (PCA), and cluster analysis. The results indicated that low-temperature stress significantly induced membrane lipid peroxidation and osmotic compensation in the shoots. PCA revealed four principal components—osmoregulation potential, cell membrane damage threshold, cold-protective protein synthesis, and membrane stability—with a cumulative variance contribution rate of 79.47%. Correlation analysis revealed no significant correlation between LT₅₀ (reflecting thermodynamic survival capacity) and the recovery growth rate (reflecting poststress regenerative capacity), suggesting that “passive endurance” and “active recovery” in sweet cherries are two relatively independent physiological processes. The comprehensive evaluation model classified the 16 cultivars into four cold-tolerance tiers: High Tolerance (Russia 8, Reid, Pacific Red, and Brooks); Moderate-High Tolerance (Tieton, Jiahong, Sandra Rose, and Early Lory); Moderate-Low Tolerance (Luyu, Rocket, Tamara, Lapins, Frisco, and Taisho-nishiki); and Sensitive (Summit and Kordia). The four-dimensional evaluation model developed in this study provides a scientific basis for cultivar selection in cold regions and offers a theoretical reference for the trade-off of traits in future molecular breeding for cold resistance in cherries.

The optimal branch bending angle for Pyrus sinkiangensis Yü (Korla fragrant pear) remains undefined. In this study, the optimal angle was determined by integrating the phenological, nutritional, hormonal, and fruit-quality responses across a 15-day bloom window. Four branch angles (40°, 60°, 80°, and 100°) were applied to 8-year-old trees in spring 2022, and flowering dynamics, bud carbon/nitrogen status, leaf morphology/mineral content, fruiting-shoot architecture, endogenous hormones, and fruit quality were comprehensively evaluated. The 80° angle maximized the fruit set (11.77%) and bud soluble sugar content (8.84 mg/g DW), significantly outperforming the other angles (p < 0.05). The flowering rate peaked at 100° (7.89%) but was statistically comparable to that at 60° and 80° (p > 0.05); calyx removal was greatest at 60° (73.33%), with no significant difference from that at 80° (71%, p > 0.05). These reproductive benefits aligned with enhanced leaf source capacity—80° pulling resulted in the greatest leaf area (59.51 cm²), the greatest amount of chlorophyll (3.11 mg/g DW), and elevated N/Mg/Cu concentrations. Branch architecture was optimized at 80°, with the percentage of medium fruiting spurs reaching 41.1% and the xylem:phloem dry-weight ratio peaking at 1.78, indicating the development of efficient assimilate transport pathways. Hormonally, 80° triggered a distinct cascade: a transient GA₄/GA₇ surge (50.6 and 1.34 ng/g DW) on 28 April, followed by sustained IAA elevation (2.05 ng/g DW) and zeatin stabilization (0.27–0.29 ng/g DW) during ovary development. Consequently, the fruit quality was comprehensively improved at 80°—the single-fruit weight (110.7 g), soluble sugar content (10.08 mg/g DW), and sugar/acid ratio (17.08) were greatest, whereas the stone-cell content was lowest (0.49 mg/g DW). Principal component analysis of 57 traits confirmed 80° as the system-wide optimum (D = 0.718). These results demonstrate that an 80° bending angle synchronizes carbohydrate supply, hormone signaling, and fruit quality in Korla fragrant pear, providing a low-cost, nonchemical benchmark for precision canopy management in high-density orchards. An 80° branch-bending angle optimizes carbon-hormone synergy via a transient GA₄/GA₇ surge and sustained IAA-zeatin signaling, maximizing fruit set and quality in high-density Korla fragrant pear orchards.