TORBEN HEDEGART
TORBEN HEDEGART is a Danish forest geneticist who has worked in Thailand for several years and is now in charge of the Thai-Danish Teak Improvement Centre. This centre was first proposed by FAO'S Teak Subcommission, which was established in 1966 and incorporated in 1967 into the Committee on Forest Development in the Tropics.
Numbers in parentheses apply to the references.
The initiation of the Thai-Danish Teak Improvement Centre, established as a project under the Danish bilateral aid programme, was described in The Natural History Bulletin of the Siam Society in 1966, where also the first working programme for the project appeared (11). When the first three-year period of cooperation had expired, the option in the agreement between the two governments for an additional period of two years was taken up. When that period ended (25 January 1970) a new intergovernmental agreement was made for another five-year period.
This paper attempts to give a progress report after the first five years and present a revised working programme for the future.
Although article one in the first - and second - government agreement mentions silvicultural as well as genetic research, our efforts in the first five years, for various reasons, have been concentrated on genetic research.
An outline of the first working programme is given below:
A. General purpose: The improvement of teak in respect of vigour, form, wood qualities, and resistance to pests and diseases.B. To outline and bring into operation a programme of selection and breeding comprising:
1. The provision of material for breeding and for the study of variation by a) selection of plus trees and subsequent vegetative propagation and b) by setting up provenance and progeny trials.2. Studies of the variation of different biological characteristics such as growth rate, flowering,
branching habit, seed production, fluting, and wood qualities, all of which may be of importance for the improvement of teak.3. Controlled pollination and subsequent execution of crossing series.
4. The setting up of a registration system and advice on experimental procedures.
C. To advise on and support the organization of seed collection, distribution and utilization, by means of:
1. Selection and demarcation of the best stands for seed collection, both in the mixed teak forests and in plantations.
2. Establishment of clonal seed orchards.
3. Investigations and improvement of nursery practice.
4. Investigations of storage and treatment of seed.D. To encourage cooperation, including exchange of material, with tree breeding stations outside Thailand, with other fields of research, with forestry education and with practical forestry. Furthermore, the centre might support the breeding of tree species other than teak.
The results obtained through this working programme are presented hereafter. To facilitate comparison with the revised working programme presented later, the above outline is not followed precisely.
SELECTION AND PROPAGATION
Selections of phenotypically superior trees - plus trees - for testing and further breeding have been undertaken since the first stages of the project.
Our selections have taken place in the natural forests as well as in plantations. In the natural forests the selection work has often had the character of a race between the geneticist and the felling saw.
Our selections have all been restricted to Thailand, and they cover by and large all teak-bearing regions of the country. So far 56 plus trees have been selected and propagated in multiplication gardens. Many of the trees have also been propagated in clone collections and clonal seed orchards. Thirty-one of our plus trees were selected in plantations-the oldest 59 years old-and of these 15 were selected for their apparent resistance to the teak beehole borer (Xyleutes ceramicus Walker), the larvae of which are ruinous to many plantation plots. For experimental and demonstration purposes a few inferior phenotypes minus frees- were included in the clone collections.
The technique used for vegetative propagation is bud grafting or "budding." In the beginning the so-called "forkert" method adopted from rubber research was applied (3, 9, 10). However, the buds produced on the young ramets in our multiplication gardens are somewhat more difficult to handle than buds originating from older material such as plus trees. The buds collected from older material are mostly small, dormant buds, whereas the buds produced in the multiplication gardens are bigger and succulent, and very likely to bruise when budded by the forkert method, in which the bud patch is covered completely by a bark flap. The budding now used is a modification of the forkert method, and can be called open-two-flap budding: A piece of bark is removed from the stock, two flaps are loosened, one above and one below the removed bark piece. The bud patch is inserted with the bud between the two flaps (see Figure 1). This method has proved significantly better than the closed forkert method.
The budding period used for the first two years was early spring, just before the rains start in April/May. This period is excellent for budding. The bark flaps are easy to loosen, the bud patch unites quickly with the stock, and the ramets get a good start with the onset of the rains. However, this period presents a few disadvantages. Besides being rather short (2-3 weeks) the good budding period is a busy time with other activities such as field plantings and the nursery preparation. Another serious drawback for spring budding is that the buds in the multiplication garden tend to be mature, that is, ready for budding, before the stocks. If the budding is delayed, the young buds in the multiplication garden will start to sprout and thus become very vulnerable and difficult to handle.
For these reasons autumn budding (November/December) has been introduced (3). The autumn has the following advantages: it gives a longer budding period (about 11/2 months), it does not coincide with other field activities, and there is no danger of the buds starting to sprout too soon. While the spring-budded stocks are cut back about 10 days after the budding operation and ramets start to develop right away, the autumn buddings remain dormant until the following spring, when the cutting back is done.
A technique for propagating teak by means of cuttings is in progress. However, with our present technique - wax sealed branch cuttings, inserted in ordinary seed beds, covered by polythene foil and watered manually - cuttings cannot compete with the simple and usually very successful budding. Furthermore, budding gives a better bud economy, as the scion used for one cutting contains buds for 3-4 buddings.
CLONE COLLECTIONS
In clone collections-or tree shows-the selected material, the plus trees, are brought together and propagated for testing under uniform environmental conditions.
The first teak clone collection in Thailand was established by cooperation between Thai and Danish foresters in 1959, six years before the initiation of the Teak Improvement Centre (1, 11, 12). This first clone collection, consisting of 11 clones, is still being assessed annually by the centre. Apart from a successful demonstration of the possibilities of vegetative propagation of teak, the most encouraging observation concerns the two clones V 7 and V 8, selected as late and early flowering respectively (7, 12). Initial flowering in teak usually occurs from the terminal bud. Hence early flowering tends to cause irregularity in stem form, shorter clear bole and lower total height. In January 1970 the difference in average heights between the two clones, originating from the early flowering V 8 and the late flowering V 7, amounted to 2 metres (see Figure 2).
FIGURE 1. - Budding of teak by "open-two-flap" technique.
A highly interesting investigation on possible clonal variation in chemical wood properties is under way, based on bore cores from this first clone collection. The technique of analysis was developed in Germany. It determines by means of paper chromatography the contents of caoutchouc, techtoquinone and desoxylapacol, the chemicals reported to be the most important constituents for the durability of teak wood (13).
A second clone collection consisting of 20 clones was established in 1965. Some of the clones are replicates from the first clone collection. This collection too is measured annually and kept under close observation for possible clonal variation. The development of the highest and the lowest clones is shown in Figure 3. Although the variation in height growth between the clones may not be striking, it will be noticed that both the early flowering V 8 and the minus tree clone V 31 are short.
FIGURE 3. - Clone collection No. 2. Development of beet and poorest clones. V 31 selected as a "minus tree," V 8 selected as "early powering."
To promote investigations on resistance to the ruinous beehole borer (Xyleutes ceramicus) a third clone collection is being established from clones thought to be resistant to this devastating pest, with controls of nonresistant clones, originating from trees attacked by the insect in various degrees. All clones included originate from Tah Chai plantation, Sawan Kalok province, where in many parts almost all trees suffer from the attack (see Figure 4). The clone collection is established near the badly-attacked plantation, and infestation should occur naturally.
SEED ORCHARDS
The first buddings in our clonal seed orchards were made in April 1966 on stocks planted the previous year. The total area of the seed orchard in autumn 1969 was about 25 hectares, in which budding had been completed on about 11 hectares. Clearings for seed orchards to be planted with 1970 root stocks total about 20 hectares. Most of the orchards are located in Payao district, Chiengrai province.
Our first orchards contain 16 clones. All clones are still in the process of being tested. The orchards are divided in blocks of 12 × 16 rows, and clone numbers appear in randomized rows. The block design was chosen in order to ease registration and to allow for statistical analysis of collected data in the process of evaluation of the clones. However, we have not been able to establish the orchards as uniformly as first expected. The establishment was spread over two to three years, and the idea of using statistical analysis on collected data must therefore be abandoned. On the whole data collected in seed orchards are of dubious value in the evaluation of our clones.
Based on results from the flowering and pollination investigations, revealing teak as an insect-pollinated species, the unit of randomization is now a single ramet, not a row of ramets of the same clone. This design also minimizes the risk of self-pollination.
Spacing in the first orchards was originally 3 × 3 metres, with one stock per point. This spacing has been found to be far too dense, and thinnings before onset of flowering have been necessary in one of the orchards to ensure good development of tree crowns.
Flowering has occurred from a few ramets in 1967, 1968 and 1969, but no seed of any significance has yet been harvested.
SEED SOURCE AREAS
As seed sources for the first 15 to 20 years until the seed orchards start producing seed of any significance, the first working programme for the centre suggests establishment of seed source areas in plantation plots and natural stands of superior qualities. Because of the shortage of staff this project has progressed little as other tasks were given higher priority. However, some areas in natural stands have been selected by the Forest Industry Organization and some by the Royal Forest Department. According to the Royal Forest Department the costs of managing this job have been considerably higher than expected.
FLOWERING AND POLLINATION
Investigations on flowering and pollination have been performed every season since 1965. The results of the 1966 investigation are reported in Silvae Genetica (4). The results are summarized as follows: It appears that the flowering period of the individual flower is one day. Emasculation and isolation may be carried out for approximately one hour after the flower has fully opened. The early afternoon is the best time for pollination.
"Insects were found to be the principal agents of natural pollination, although some wind pollination may take place. Teak is mainly a cross-pollinating species, but fruits after self-pollination occur. The germination of these is poor compared to that of fruits resulting from cross-pollination. Apomixis has not been observed."
The following three seasons' work largely confirms the 1966 results. The fertilization percentage in open pollination has been found to be less than 1 percent, while controlled cross-pollinations have had an average success of about 12 percent. However, there are indications that individual variation in ability to set seed is considerable, whether after controlled cross- or self-pollination or after open pollination. Also germination percentages of seed resulting from crossings and selfings point to significant individual differences.
PROVENANCE RESEARCH
Two collections of seed ¹ for provenance trials were made. Both collections are restricted to Thailand. We have had no opportunity to include foreign seed in our trials, apart from one seed sample obtained through a commercial nursery in India and included in the nursery trial of the 1968 collection.
(¹ The term "seed" is used in this paper because it seems to be widely accepted. The term "fruit" would be more correct, as teak forms stone fruits containing as many as 4 seeds.)
Our first collection was made in 1966. Varying amounts of seed were collected from 63 localities. Unfortunately the seed was sown unreplicated in a rather heterogene nursery, so that no reliable nursery results are available. In 1966 stumps were sufficient for one field trial including 30 provenances. The trial was planted at Huey Tak teak plantation, Lampang province. After the first growing season survival percentages showed no significant differences (probability [p] =0.05), whereas significant height differences occurred. Later measurements show that the statistical significance observed in the first year heights is no longer present. Development of the two highest and the two lowest provenances compared to mean height of the trial is shown in Figure 6.
In 1967 two-year-old stumps from the 1965 seed collection were available from 30 provenances, of which 19 were replicates from the 1966 field trial. This trial, which was planted at Kiu Tup Yang, Chiengrai province, has developed poorly and unevenly, and has so far not displayed intelligible results.
A second seed collection including 16 provenances was made in 1968. Three to six kilogrammes of seed were collected per sample. An examination of the seed revealed considerable variation in size and weight. A nursery experiment indicated highly significant differences in germination percentages (p = 0.01) and significant differences in size of seedlings (p = 0.05). In 1969 stumps were sufficient for a series of four field trials. The trials were planted along a line from north to south in the provinces of Chiengrai, Uttaradit, Nakhon Ratchasima and Chantaburi respectively. The first year's results from the four trials show significant differences (p = 0.05) in survival and height, but the picture of site/provenance interaction is still ambiguous.
FIGURE 6. - Provenance trial at Huey Tak teak plantation, Lampang province, Thailand. Development of the two highest and two lowest provenances compared to mean.
NURSERY RESEARCH
A number of nursery experiments were carried out, the main results of which are summarized as follows.
Pretreatment of seed: Removal of the exocarp prior to sowing will improve the germination percentage, speed germination and give more uniform germination, hence more uniform seedling size. For smaller quantities of seed the "white ant" treatment has proved successful; that is, the seed is exposed to white ants that will remove the exocarp. For larger quantities of seed, the ant treatment is not reliable and a machine has been constructed for the job. The machine is still in the experimental stage but results so far are encouraging (see Figure 7). It works by grating the seed between two discs with adjustable spacing. For smaller quantities of seed, the Danish/FAO Forest Tree Seed Centre in Denmark has had good results with a potato-peeler of the rotating type.
Sowing experiments have shown that the traditional dense sowing-about 1 500 seed per square metre- gives a very poor utilization of the seed. Less dense sowing is recommended, but the optimum sowing rate must be calculated from cost of seed versus cost of nursery operations. In our own experimental nursery - experiments on grading, shading, watering, weeding, etc., and sowing of provenance trials-we generally sow at a rate of 100 seed per square metre.
Aiming at mechanization of nursery operations, an experiment is being carried out on sowing in rows of fixed spacing, but with a variable seed spacing in the rows.
An experiment on sowing in pots of various sizes and materials is under way. The potted plants are not intended for establishment of ordinary plantations; but for the establishment of clone collections and clonal seed orchards, pre-budded, potted stocks would be a great advantage.
Watering experiments indicate that watering in dry periods of the rainy season is valuable, while watering in the cool and dry seasons seems of no significance.
Fertilizer experiments show that teak seedlings may react positively to Ca and NPK treatments and combinations of these.
A minor experiment indicates that early lifting of stumps and their storage in fresh sawdust until planting can be done with relatively small loss of viability. Storing for 36 days - 18 April to 24 May 1968 - resulted in reduced survival of 14 percent. Investigations on early lifting and storage of stumps are being intensified.
REGISTRATION AND FILING
At the very start of the project a fundamental task was the establishment of a registration and filing system. Furthermore, standard rules for experiment descriptions and reporting had to be compiled.
Most of the standard forms for registration first introduced, such as "Plus tree record form," "Propagation card" and "Seed lot card" have proved relatively practical. However, alterations and additions may be wanted in the future. We have in mind especially the scoring system used in the " Plus tree record form" (8). It is very likely that more detailed knowledge concerning clonal variation in chemical and technical wood characters will give rise to a desire to include a description of these characters in the record form.
TRAINING AND COOPERATION
Training of Thai counterparts is a major aspect of the project. During the first five-year period no regular training course was run, and only a few lectures were given. A number of Thai foresters-with university training as well as at ranger level- have joined the centre and have, through the daily work. gained some experience in forest tree improvement.
Three Thai foresters have received technical training in Denmark for five months.
Besides the foresters directly attached to the project, the centre has cooperated with a great number of foresters throughout the country. The interest in the centre's activities has been keen, and in general collaboration with local forestry people has been easy.
The international cooperation called for in the first working programme for the project (11) still leaves a lot to be desired. During the period of the project only one batch of seed was obtained from abroad, the germination of which was very poor. The Royal Forest Department in Bangkok is willing to exchange forest tree seed with other countries and it is hoped to establish new provenance trials covering the full range of the species outside, as well as inside, Thailand. The activities of the new Danish/FAO Forest Tree Seed Centre should do much to ensure an efficient exchange of seed with other major teak-growing countries, such as India, Burma and Indonesia.
Based on the results and experiences obtained through the first five-year period of the project, a revised working programme has been established and is outlined below.
The programme may seem rather ambitious, and it is realized that without cooperation from many institutions, national as well as international, it has no chance of being carried through.
Outline of second working programme:
A. PROVENANCE RESEARCH
Our activity in this field will be intensified. International cooperation is imperative, and in this connexion our centre sets its hopes on the newly-initiated Danish/FAO Forest Tree Seed Centre.
B. BREEDING
In the vast and complex field of breeding, we hope for closer cooperation with other breeding centres. We would very much like to see this cooperation materialize in exchange for knowledge as well as selected material for further breeding. Without very close cooperation with entomologists and wood chemists and technologists, investigations on pest resistance and wood properties are not possible. We have in mind especially the very urgent investigations on resistance to the ruinous beehole borer and the examination of possible clonal variation in technical and chemical wood characteristics and the importance of these for the quality of teak wood.
1. Selections will be concentrated in plantations, and wood qualities may be included in our selection criteria.2. Vegetative propagation. Improvement of the technique will be attempted through production of better root stocks.
3. Clone collections. More care will be taken to ensure uniformity in the establishment. Design will be altered to allow for statistical analysis of collected data.
4. Seed orchards. The area of clonal seed orchards will be considerably increased. The first seed lots harvested will be used in polycross tests.
5. Seed source areas. Emphasis will be put on selection of plantation plots of superior qualities.
6. Flowering and pollination. Many questions still remain unanswered. Emphasis is put on increasing the speed of the operation of controlled pollination. Time-consuming crossing series are foreseen.
C. SILVICULTURAL RESEARCH
Silvicultural research is an important part of the improvement programme, and closely related to our efforts in breeding. Our activity in this field will be drastically intensified.
D. NURSERY RESEARCH
Optimum exploitation of seed in the nursery is of special interest in view of our breeding programme, and the importance of continued and intensified nursery research is recognized. It is our hope that a major part of the nursery research work can be attended to by the Northern Nursery Centre.
E. LABORATORY RESEARCH
For more complex laboratory research work our centre will have to depend, for the time being, on already established and staffed laboratories.
F. EDUCATION OF COUNTERPARTS
The educational part of our project is of vital importance. More direct training will be adopted at the centre, and postgraduate studies are no longer limited to Denmark.
G. ADOPTION OF OTHER SPECIES IN THE RESEARCH PROGRAMME
Teak is by far the most economically important timber species in Thailand, and adoption of other species in our improvement programme must be based on painstaking survey and evaluation.
(1) BOONKIRD, SA-ARD. 1964 Progress report On the first teak tree-show in Thailand. Natural History Bulletin of the Siam Society, 20 (4).
(2) BRYNDUM, KNUD. 1966 The germination of teak. Natural History Bulletin of the Siam Society. 21 (1 and 2).
(3) BRYNDUM, KNUD. 1969 Budding of teak. Indian Forester, 95 (3).
(4) BRYNDUM, KNUD & HEDEGART, TORBEN. 1969 Pollination of teak (Tectona grandis L.). Silvae Genetica, 18 (3). 57-96.
(5) CHAIGLOM, DUMBONG. 1966 Teak beehole borer and the control research in Thailand. Vanasarn, 24 (3)
(6) CHATTERJEE, P.N. & SEBASTIAN, V.O. 1965 The feeding habits of larvae of Hapalia machaeralis, the teak leaf skeletonizer on the leaves of Lantana camara Linn., and a suggestion for evolving a new insecticide. Indian Forester, 91 (3)
(7) GRAM, K. & LARSEN, C. SYRACH. 1958 The flowering of teak (Tectona grandis) in aspect of tree breeding, based on observations in Thailand. Natural History Bulletin of the Siam Society, 19.
(8) KEDHARNATH, S., RAMANTHA CHETTE, C.K. & RAWAT, M.S. 1969 Estimation of genetic parameters in teak (Tectona grandis) without raising progeny. Indian Forester, 95 (4).
(9) KEIDING, HENRIK & BOONKIRD, SA-ARD. 1960 Budding and grafting of teak. Document, third session of the Teak Subcommission, New Delhi, India, 1960. FAO/TSC 60/3.3.
(10) KEIDING, HENRIK. 1961 Budding and grafting of teak (Tectona grandis). Natural History Bulletin of the Siam Society, 20.
(11) KEIDING, HENRIK. 1966 Aim and prospects of teak breeding in Thailand. A programme of work for the Thai/Danish Teak Improvement Centre at Mae Huad Teak Plantations. Natural
History Bulletin of the Siam Society, 21 (1 and 2).
(12) LARSEN, C. SYRACH. 1966 Genetics in teak (Tectona grandis). In Royal Veterinary and Agricultural College. Yearbook 1966. Stockholm.
(13) SANDERMAN, WILHELM & SIMATUPANG, MARULI H.1966 Zur Chemie und Biochemie des Teakholzes (Tectona grandis L. fill). Holz als Rohund Werkstoff, 24 (5).
