Comprehensive evaluation of abiotic stress tolerance and graft compatibility of Citrus junos cv. 'Shuzhen No.1'

Citrus is one of the world's most economically important fruit crops cultivated by grafting. To support the growth of scion cultivars, rootstock is the primary source of resistance to various abiotic stresses. Herein, seedlings of two genotypes of Citrus junos Sieb. ex Tanaka (the novel rootstock 'Shuzhen No.1' and commonly used rootstock 'Ziyang Xiangcheng'), as well as three commonly used rootstocks including citrange (Citrus sinensis Osbeck. × Poncirus trifoliata Raf.), trifoliate orange (P. trifoliata), and red tangerine (Citrus tangerine Hort. Ex Tanaka), were used as testing materials. The seed characteristics were evaluated, and the rootstock seedlings were subjected to flooding, drought, alkaline, and freezing treatments. Over time, the contents of chlorophyll, soluble sugar, proline, malondialdehyde, and the activity of superoxide dismutase, peroxidase, and catalase in the leaves under different treatments were examined. Furthermore, five citrus varieties were grafted as scions onto one-year-old seedlings from the four rootstocks. Graft success, shoot growth, and leaf greenness were measured and compared. The physiological and biochemical changes in 'Shuzhen No.1' were found to be similar to those in 'Ziyang Xiangcheng'. 'Shuzhen No.1' exhibited greater tolerance to flooding, alkaline, and freezing stress compared to the other four widely used citrus rootstocks, as indicated by physiological and biochemical indexes and principal component analysis. Moreover, the five citrus varieties grafted onto 'Shuzhen No.1' demonstrated vigorous growth and tree vigor. These findings provide valuable insights for the application of 'Shuzhen No.1' and future research on citrus rootstock.