If we plant a seed from a good apple the tree it produces will bear apples, which may be much different from the tree whose seeds were sown. So to produce an identical tree the only method is grafting or budding. In these processes scion/bud is taken from a tree to be cloned and is grafted/budded onto other tree’s roots. These roots are called ‘ROOTSTOCK’. Apple trees do not grow on their own roots but propagated on rootstocks which control the size/vigor of the tree. It is necessary to choose the right type of rootstock according to your needs.
There are two types of rootstocks:
- Seedling Rootstocks
- Clonal Rootstocks
These rootstocks are grown from the seeds of the apple we eat. They have the capability to make a vigorous tree with very deep roots which are adaptable to poor soils. The performance of seedling root is variable; some of them perform well whereas some of them fail to perform good because they are produced from seed and every seed have different character and quality. Apple trees on seedling rootstocks are usually vigorous and come very late into production. Hence, for seedling rootstocks, there is genetic variability which exists with respect to variable root structure, variable tolerance limits to environmental stresses and variable susceptibility to different root pests.
To overcome these problems most of the apple orchards in world are propagated on clonal rootstocks. Clonal rootstocks are identical to a mother rootstock with some desired characteristics such as disease resistance, tolerance to environmental factors and controlled tree size. Most of the clonal rootstocks used today are derived from the collections by East Malling Research Station in England. The “M” prefix refers to the East Malling Research Station, England. The “MM” prefix, Malling Merton, refers to hybrid trees of the Malling series crossed with “Northern Spy” in Merton, England. Some rootstocks have EMLA suffix, which refers to East Malling/ Long Ashton. EMLA rootstocks were made with a program to eliminate viral pathogens.
WHY CLONAL ROOTSTOCKS?
- Apple trees propagated on seedling rootstocks lack in fruit quality and production with time.
- Apple trees on seedling rootstocks come late into production.
- Apple trees propagated on seedling rootstocks have a large tree size, hence more labour is required for tree maintenance and fruit harvesting.
- Apple trees propagated on seedling rootstock have genetic variability; each tree has different performance levels.
- Apple trees propagated on clonal rootstocks starts bearing apples in 3-4 years.
- Apple trees propagated on clonal rootstocks helps in uniform quality; colour and size of fruit.
- There is more production in small field when trees are propagated on clonal rootstocks.
- By using clonal rootstocks one can control the vigor of the tree.
- Suitable rootstocks can be planted accordingly with respect to the environmental factors, disease resistance, root structure and soil factors.