Nearly all commercial citrus trees are grafted, and the rootstock has a major effect on the performance of the scion cultivar. A citrus tree’s resistance to or tolerance of disease, nematodes, salt, cold, and other factors may be influenced by the rootstock. Also, the rootstock affects the tree’s adaptability to various environmental factors, as well as the quantity and quality of fruit that it produces. No available rootstock possesses all of the desirable traits needed by the citrus industry. Also, changes in culture and production problems create new demands.