Comparative Analysis of Sugar-Starch Profiles in Northern and Southern Chinese Chestnuts Grafted Northward

Soluble sugar and starch are crucial quality attributes of chestnuts. In this study, four chestnut cultivars from distinct geographical origins were grafted onto uniform rootstocks in a common orchard. For each cultivar, three mature fruits were collected from each of three independent trees (biological replicates) and analyzed for soluble sugar and starch contents, with sugar composition profiled by gas chromatography-mass spectrometry (GC-MS). In this study, we aimed to elucidate inter-cultivar variations in sugar metabolism and provide theoretical insights into regional adaptation strategies. The results revealed that the southern-origin cultivars 'Liu Yue Bao' (LYB) and 'Nong Da 1 Hao' (ND1) had significantly higher soluble sugar levels (95.8 g/kg and 92.4 g/kg, respectively) than the northern-origin cultivars 'Yan Long' (YL, 74.6 g/kg) and 'Huang Peng' (HP, 83.8 g/kg). Conversely, starch content was markedly lower in LYB (577.6 g/kg) and ND1 (584.2 g/kg) than in YL (620.1 g/kg) and HP (601.7 g/kg). Amylose ranged from 149.7 g/kg to 182.3 g/kg of the total starch. Correlation analysis demonstrated a strong positive association between total soluble sugar and sucrose contents (r = 0.87, p < 0.05), whereas starch exhibited significant negative correlations with all detected saccharides. GC-MS profiling identified 20 saccharides across cultivars, with sucrose dominating, followed by maltose, inositol, glucose, raffinose, d -galactose, and d -fructose. Notably, levoglucosan was detected only in the southern cultivars under the conditions tested. Comparative analysis of the northern (YL, HP) and southern (LYB, ND1) cultivars revealed differential accumulation of nine saccharides. These findings advance the existing understanding of geographical variations in chestnut sugar composition and can inform cultivar selection for cross-regional cultivation. • Southern cultivars grafted in the north had more soluble sugar than northern ones • Southern cultivars grafted in the north had lower starch content than northern ones • Levoglucosan was found only in the southern chestnut cultivars • Southern cultivars grafted in the north had more amylose than northern cultivars