1-Rootstock’s speciality of dwarfness (Genetic). They are also called clonal rootstocks. They are categorized according to their dwarfness levels: Dwarfs: M9: (requires support;reaches up to 2.5 m; gives good results at low temperatures; resistant to crown rot disease and vulnerable to bacterial crown gall:
M26: Consists of trees slightly bigger than M9 Semi-dwarf rootstocks: M7, MM106: Normal seedlings form trees as big as 50% of the trees. This tree is quite resistant to fire blight disease. There are other strong rootstocks such as M2, M111, M16, M15, M25, M109, and MM104...
2- Variety’s Speciality of Dwarfness: They are varieties that grow dwarf. They are called spur varieties. For instance: Spurstarkcrimson, Spurstark Golden etc. Gardnes should not be formed with seedlings which are grafted on dwarf rootstocks with spur varieties. Studies show that it reduces yield and quality.