PJB-2026-91
Photosynthetic and Fruit Characteristics of Five Malus spectabilis Varieties from the Yili River Valley: Implications for Horticultural Germplasm Utilization
Jiaqi Cao
Abstract
Malus spectabilis, a dual-purpose horticultural species valued for ornamental and edible traits, is widely cultivated in the Yili River Valley (Xinjiang, China). However, post-pruning regrowth and the coordination between photosynthetic capacity and fruit development—key processes for its horticultural utilization—remain underexplored, limiting elite cultivar selection and cultivation optimization. This study aimed to determine intervarietal differences in leaf photosynthetic traits, fruit phenotypic/quality characteristics, and their correlations, and to identify optimal varieties for targeted horticultural applications.
The experiment was conducted in an open field within the Yili River Valley using five M. spectabilis varieties (M. ‘Xifu’, M. ‘Gaozhi’, M. ‘Wangzhu’, M. ‘Hongye’, M. ‘Chuisi’). All 3-year-old trees were uniformly pruned to 2.5 m height and 1.8 m canopy width in March 2024 to eliminate light interception variability. During peak fruit ripening (mid-September 2024), fruit phenotypic traits (color, size, edible rate) and quality indicators (soluble solids, soluble sugar, vitamin C, total flavonoids) were determined, while leaf photosynthetic pigments (chlorophyll a/b, carotenoids) and gas exchange parameters (net photosynthetic rate, transpiration rate, stomatal conductance) were measured using a UV-Vis spectrophotometer and portable photosynthesis system, respectively. Data were analyzed via one-way ANOVA and Pearson correlation analysis.
Results showed that exogenous pruning (uniform canopy management) significantly standardized inter-tree growth conditions, yet intervarietal differences in target traits remained prominent. For fruit phenotypic traits, M. ‘Gaozhi’ exhibited the largest single fruit weight (15.38 g), transverse diameter (32.62 mm), and edible rate (95.59%), while M. ‘Hongye’ had the highest water content (30.73%). In terms of fruit quality, M. ‘Wangzhu’ had the highest total flavonoid content (6.36 mg·g⁻¹); M. ‘Hongye’ outperformed others in soluble solids (8.24%), soluble protein (2.86 mg·g⁻¹), and solid-acid ratio (28.48%); and M. ‘Chuisi’ showed the highest soluble sugar (4.82%), vitamin C (4.58 mg·g⁻¹), and sugar-acid ratio (16.56%). For photosynthetic traits, M. ‘Hongye’ had the highest chlorophyll a content (17.22 mg·g⁻¹), M. ‘Xifu’ the highest chlorophyll b content (5.62 mg·g⁻¹), M. ‘Wangzhu’ the highest total chlorophyll (18.46 mg·g⁻¹) and carotenoid content (3.83 mg·g⁻¹), and M. ‘Chuisi’ the highest net photosynthetic rate (6.70 µmol CO₂·m⁻²·s⁻¹). Correlation analysis revealed significant associations: total chlorophyll content was negatively correlated with net photosynthetic rate (r = -0.65, p < 0.01), while fruit size-related traits (single fruit weight, transverse diameter) were negatively correlated with soluble sugar (r = -0.75 to -0.88, p < 0.01) and vitamin C content (r = -0.70, p < 0.01), indicating a trade-off between fruit biomass accumulation and nutrient synthesis.
This study demonstrates that uniform pruning enhances the reliability of intervarietal trait comparisons, and identifies M. ‘Gaozhi’ (suitable for fresh consumption/dual-purpose breeding), M. ‘Hongye’ (ideal for juice processing), and M. ‘Chuisi’ (promising for functional food development) as elite M. spectabilis germplasm. The observed correlations between photosynthetic and fruit traits provide a scientific basis for optimizing cultivation practices (e.g., targeted fertilization to balance photosynthetic efficiency and fruit quality) and guiding future breeding programs for M. spectabilis in the Yili River Valley.
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