Arboretum., Horsholm, Denmark
Kasetsart University, Bangkok, Thailand
VEGETATIVE propagation is a most important implement in the hands of the forest tree breeder and the progress of his breeding is to a large extent dependent on whether he succeeds in finding a method which suits the species and the conditions he is concerned with. C. Syrach Larsen in Volume 5, Number I and lately François Mergen in Volume 13, Number 2 of Unasylva have stressed the importance of vegetative propagation for the work in forest tree breeding.
Teak (Tectona grandis) is of course no exception and in the spring of 1959 investigations were made in Thailand in order to find a suitable method of vegetative propagation for this species. The investigations were a result of a Thai-Danish botanical co-operation and were supported by the Danish Expedition Fund, If a practical method could be found, the intention was to establish a clone collection and thereby make way for breeding of teak on a larger scale.
In the current investigations only the so-called forkert budding method was employed. This method is used extensively for budding of rubber (Hevea brasiliensis) and it was assumed that it might also suit teak.
Two vertical incisions forming a pointed arch are made on the rootstock. The rind flap thus made is lifted where the cuts meet, exposing the cambium of the stock (Figure 1). A budpatch, i.e., a rectangular piece of bark containing one bud from the selected tree, is placed on the exposed cambium and the flap pushed back. The union is covered with a rectangular piece of palm leaf which is tied firmly to the stock beginning from below and going upward. Finally, the budding is shaded with some large leaves fixed to the stock above the union.
FIGURE 1. Insertion of budpatch on rootstock.
The completed budding is left for a week or more depending on the species before opening takes place. After that time the budpatch and usually the flap have grown to the stock. At opening the And flap is cut off exposing the budpatch. Some time after opening, when the callus has hardened and one is sure the budpatch is still alive, the stock is cut back.
The actual budding took place at the end of April and the beginning of May 1959 at the Huey Tak teak plantation in northern Thailand, It was hoped that the budding could be carried out in the nursery, but due to low rainfall the previous year almost all the seedlings were too small for the purpose. A suitable area was then sought for in a 1958 planting also used for stocks of one-year-old seedling stumps (two years from wed and one year from planting in the field). The size of the stocks varied considerably, but the average diameter at budding height was about 3 centimeters. All the seedlings had developed new leaves at the time the budding began, which means that the resting period during the dry season was finished.
Budwood was out from 11 selected trees, both in natural stands of mixed teak forest and from the plantation. The age of the selected trees ranged from 13 to 90 years. Each tree was budded on 15 to 25 stocks depending on the stocks available at the experimental site.
The timetable for the budding procedure was, briefly, as follows:
1. Insertion of budpatch - removal of cover and flap:
2. Removal of cover - cutting back of stock:
3. Cutting back - sprouting of budding:
The total time between insertion of budpatch and the sprouting of the bud (Figure 2) is thus about three weeks, which is half the time for the same operation in rubber.
FIGURE 2. Budding of teak on the point of sprouting.
It soon became obvious that the callus formation on the stocks was very active. We found that a budpatch would grow to the stock after only four days from insertion. The result of the budding was most satisfactory. On an average, for 11 clones 80 percent of the buddings succeeded and began to sprout before the end of May. Some of the first buddings we made had grown 25 centimeters in three weeks from the time of sprouting. As a matter of fact, the shoots deriving from the inserted buds seem to behave in the same manner and grow with the same vigor as adventitious shoots from a stump.
Approximately 200 successful budgrafts were the result of these initial investigations. They have been followed closely during the first growth season and measured monthly, the last time in December when the rainy season stops. Three buddings had died due to termites, but the rest had reached an average height of 1.78 meters. Some clones measured 2.26 meters and were almost as high as the seedlings in the area surrounding the experimental plots (Figure 3).
FIGURE 3. Clone SG. V after one, growth season, photographed February 1960. Note the union just over ground level an the first budgraft to the right.
It is possible that successful buddings may be increased to 90 or 95 percent, when some details have been improved and more experience gained. Even now it is thought safe to conclude, from these initial trials, that teak is easily propagated vegetatively. Teak compares favorably with rubber for which budding is used extensively not only in breeding but also in estate practice. Whether it will be feasible to do so for teak is an open question but, in any case, the 200 buddings comprising 11 clones form a clone collection or a tree show, from which useful information may be drawn to the profit of future silviculture of teak.
GRAM K. and SYRACH LARSEN, C. The flowering of teak (Tectona grandis) in aspects of tree breeding. The Natural History Bulletin of the Siam Society, Vol. 19, Bangkok, 1968.
KEIDING, H. Budding and grafting of teak. FAO/TSC-60/3.3. New Delhi, 1960.