Scion root pruning affects leaf C/N ratio and physiological performance of ‘Shiranuhi’ mandarin trees grown in a greenhouse

Intensive scion rooting in ‘Shiranuhi’ mandarin [(Citrus unshiu × C. sinensis) × C. reticulata] trees contributed to reduced flowering, yield, and fruit quality at commercial mandarin orchards. To elucidate the effect of a cultural technique on controlling the loss of fruit quality and yield, mandarin trees were grouped into three treatments as follows: no scion root (without scion roots), scion root intact, and scion root pruning in thirteen-year-old ‘Shiranuhi’ mandarin trees. Scion root pruning reduced leaf nitrogen (N) and enhanced leaf carbon (C), thereby increasing the leaf C/N ratio in scion root pruned trees, than those with intact scion roots. Physiological responses of flowering and fruiting were significantly enhanced by pruning scion roots in mandarin trees. Fruit size, fruit fresh weight, and soluble solids content (SSC) were considerably greater in scion root pruned trees than those with intact scion roots. Furthermore, pruning scion roots increased total fruit yield than that in mandarin trees with intact scion roots. Overall, the results indicated that scion root pruning should contribute to minimizing cultural problems, such as low yield and poor fruit quality, which have been caused by scion rooting in ‘Shiranuhi’ mandarin orchards.