Study on the compatibility of a new salt-tolerant Malus × robusta ‘Yanxing’ rootstock with different apple cultivars

[Objective] Soil salinization leads to the inability of apples to grow normally, affecting the sustainable development of the apple industry. The salt tolerance of apple tree depends mainly on the rootstock. The grafting compatibility of the rootstock with scion variety is a prerequisite for normal growth. The graft survival rate is the most direct index to show the grafting compatibility in the short term. The study aimed to investigate the grafting compatibility of the salt-tolerant rootstock Yanxing with apple cultivars. [Methods] 2-years old nursery trees propagated bu tissue culture of the new salt-tolerant Malus × robusta ‘Yanxing’ were used as rootstocks.18 apple cultivars were selected as scion varieties. The survival rate of the grafting units, the healing state of the grafting unions, the height and thickness of the scion part, the thickness of the rootstock and the ratio of the thickness of the rootstock and scion of each grafting combination were recorded in the end of the first growing season. The field compatibility constant (FCC) > or < 2.0 indicated that the diameter of rootstock was too thick or thin, the grafting compatibility was poor. The comprehensive evaluation of the grafting compatibility was represented by the average membership degree. A larger average value of membership indicated a stronger affinity. [Results] The survival rates of the grafting unites of the 18 apple cultivars with the rootstock were over 90%, and the healing of grafting unions were good. Among them, the survival rate of Fuji and Changping No. 8 was 98%. The survival rate of Jinzhou Red Fuji and 12-20 was relatively low (90%). The growth of scion and rootstock was relatively balanced, showing a slight phenomenon of small feet. In contrast, the grafting unions of Jinzhou Red Fuji and Orin with the rootstock was slightly uneven, with several nodules. Among the growth indexes, the thickness of the different scion varieties had great difference, and the thickest one was Changping No. 8 and the thinnest one was Orin was. The thickness ratios of the rootstock-scion of Venus Gold, Gala and Fuji were closest to 1, while those of Jiping No. 2 and Jinzhou Red Fuji were relatively far from 1. Fuji, Venus Gold, Jiping No. 1, Changping No. 8 and Jiping No. 5 showed the best grafting affinity with Yanxing. According to the rank of average membership, Fuji had the best compatibility with Yanxing. Jiping No. 2 showed a short-term affinity phenomenon and died in the third year of growth. Orin showed the phenomenon of yellow leaves and slow plant growth in the third year after grafting. [Conclusion] Yanxing as rootstock had good grafting compatibility with most apple cultivars. The grafting compatibility of Fuji and Venus Gold with the rootstock was best. The grafting compatibility of Jiping No. 2, Jinzhou Red Fuji and Orin with Yanxing was slightly poor.