A Study of Scion Phenotypes in Pummelo Grafted onto a New Citrus Rootstock Citrus junos ‘Pujiang Xiangcheng’

Citrus is one of the most important fruit crops in the world. Citrus junos Siebold ex Tanaka cv. Pujiang Xiangcheng is a new rootstock with a good grafting affinity and multiple abiotic stress tolerance. In this study, the effects of ‘Pujiang Xiangcheng’ and two commonly used rootstocks for Citrus maxima (Burm.) Merrill cv. Guanxi Miyou, considering their growth, photosynthetic performance, phytohormones and fruit quality, were evaluated. There was little difference between three graft combinations in the height and diameter of the scions. However, the rootstock ‘Pujiang Xiangcheng’ can cause an up-regulated photosynthetic capacity. In addition, ‘Guanxi Miyou’ on ‘Pujiang Xiangcheng’ had the highest total sugar (TS) content (129.28 mg·g−1) and the lowest titratable acid (TA) content (0.78 g·100 mL−1) in 2020 and the highest TSS (11.84%) in 2021. There was no significant difference in the TSS-to-acid ratio between the fruit of ‘Guanxi Miyou’ on trifoliate orange (13.41) and ‘Pujiang Xiangcheng’ (15.68), but it was significantly higher than that of ‘Guanxi Miyou’ on sour pummelo (11.61). Moreover, the comprehensive fruit quality of ‘Guanxi Miyou’ on ‘Pujiang Xiangcheng’ was better than on sour pummelo and trifoliate orange based on two-year statistics. We suggest that ‘Pujiang Xiangcheng’ might be the appropriate rootstock of ‘Guanxi Miyou’ in production compared with sour pummelo and trifoliate orange.