Differential effects of rootstock genotype on photosynthetic parameters and fruit quality in grafted 'W. Murcott’ mandarin

The selection of a suitable rootstock is critical for sustainable citrus production, particularly in regions facing abiotic constraints like calcareous soils and cold damage. This study aimed to identify viable rootstock alternatives to the standard sour orange (C. aurantium L.) for 'W. Murcott' mandarin cultivation in the calcareous soils of Adana, Turkey. The performance of four rootstocks "Carrizo citrange (C. sinensis × Poncirus trifoliata), Volkameriana (C. volkameriana), sour orange, and Flying Dragon (P. trifoliata var. monstruosa)" was evaluated based on fruit yield, quality parameters, leaf chlorophyll content (SPAD), chlorophyll fluorescence (Fv'/Fm'), and gas exchange measurements. The results demonstrated significant rootstock-induced variation across all measured parameters. Volkameriana produced the highest fruit yield (58.33 kg/tree) and exhibited superior leaf chlorophyll content (73.63 SPAD) and photosynthetic rates. However, it yielded fruits with lower total soluble solids (TSS) and higher titratable acidity (TA) compared to other rootstocks. Carrizo citrange provided an optimal balance, ranking second in yield (48.33 kg/tree) while producing the largest fruits (151.13 g) and the highest TSS (13.63%). It also supported high photosynthetic activity and strong juice color intensity (indicated by a positive a* value). Flying Dragon consistently demonstrated the poorest performance across all metrics, including yield, fruit size, and physiological activity, attributed to its sensitivity to calcareous conditions. Sour orange performed reliably in fruit quality. Correlation analysis revealed strong positive relationships between chlorophyll content, photosynthetic rate, and yield. In conclusion, while Volkameriana maximizes vegetative growth and yield, Carrizo citrange is recommended as the most suitable rootstock for 'W. Murcott' in this region due to its synergistic combination of high yield, excellent fruit quality, and physiological efficiency.