This Field Manual is the fifth in a series of Field Manuals prepared by UNDP/FAO Project RAS/91/004, addressed to field workers in Forest Tree Improvement. It is aimed at presenting basic concepts and methodologies in vegetative propagation of forest trees in connection with Forest Tree Improvement. The Field Manual is an independent supplement to Field Manual No. 4: “Seed Orchards”.
The Field Manual refers to the three conventional macropropagation methods, viz. propagation by cuttings, air-layering and grafting. Micropropagation/tissue culture, although a way of vegetative/clonal propagation with wide use in Tree Improvement Programmes, is considered to differ so much from the conventional macro propagation methods and in itself so comprehensive, that it will be dealt with in a separate Field Manual.
The field Manual was prepared by Mr. Lars Schmidt, Associate Professional Officer, in consultation with the senior project staff.
Dr. K. Vivekanandan
Chief Technical Adviser
Los Baños, Philippines
Plants have two ways of reproduction, sexual by means of seeds, and asexually or vegetatively by means of vegetative tissue. Both ways occur in living plants in nature. In nature, some plants reproduce mainly vegetatively while others rely almost totally on sexual reproduction. For the plant breeder it is desirable to be able to manipulate sexual and vegetative reproduction (propagation) to fit into the tree improvement programme.
Genetically the two ways of reproduction differ. Seeds contain genes from the female parent (where we collect the seeds) and the male parent (which contribute the pollen and which is often unknown). Vegetative material is genetically identical to the mother plant from where it was collected. The present guide entirely deals with vegetative propagation.
There are four main uses of vegetative propagation in a Tree Breeding Programme:
The establishment of clonal seed orchards.
The establishment of clonal banks.
The propagation of special breeding material, e.g. exceptional hybrids that are lost through sexual reproduction, sterile hybrids etc.
Mass propagation of selected materials.
There are several ways of vegetative propagation. The three main types in forest tree propagation are grafting, air-layering and the use of cuttings. The three types are referred to as macropropagation, as alternative to micropropagation or tissue culture. Propagation by cuttings is the most convenient and cheapest method and usually preferred when possible. Air-layering is a variation of propagation by stem cuttings in which root formation is initiated before the plant part is separated from the mother tree. In grafting, the shoot (scion) of the desired tree is joined with a root (stock or root stock) of different genetic origin.
Which methods of propagation to be used in a particular situation is a matter of experience with the individual tree species plus the purpose and conditions of the propagation. The methodologies of vegetative propagation should be adapted to the individual plant species. The same method may work differently at a different time of the year, etc. The present guide is restricted to dealing with only the most basic methodologies and concepts, upon which the field worker may adapt his own variation according to his specific species and conditions.