GENETIC IMPROVEMENT OF BOMBACOPSIS QUINATA AT MONTERREY FORESTAL, COLOMBIA¹

by

Álvaro Vallejo, Jefe Investigación Forestal, Monterrey Forestal Ltda. A.A. 6610, Cartagena, Colombia
Email: [email protected]

INTRODUCTION

Bombacopsis quinata is a tropical tree which occurs naturally in Central and South America, from the south of Honduras to the north of Colombia and Venezuela. In Colombia, it is mainly found along the Atlantic coast (in the provinces of Sucre, Bolívar, Magdalena, Atlántico and Cesar), in central Magdalena (Santander) and in the province of Arauca. It produces one of the most valued timbers in the country and has been used intensively to produce furniture and wood carvings and all types of moulds, pieces of windmills and other objects in permanent or sporadic contact with water. Its popularity resides in the fact that it is an easy workable wood characterized by strong durability, resistance to fungal and insect damage and humidity, it has an excellent finish as well as strong dimensional stability. It does not crack or splinter and can be used with little drying.

Map 1. Natural distribution of Bombacopsis quinata

Despite the value of its wood, relatively little has been done to conserve the species within its natural distribution. Up to 1999, only 10 000 ha had been planted, mostly in northern Colombia where the wood is utilized to supply a chip board plant and where it is hoped that the wood from the final harvest will be used for plywood.

In response to the demand for wood, Monterrey Forestal Ltda. has been planting Bombacopsis quinata since 1983. Planting has, almost from the start, been supported by a research programme focused on silvicultural aspects and on selection and breeding.

The breeding programme aims to produce trees better adapted to the environmental conditions of the sites available to Monterrey Forestal, and on improved growth and stem form for plywood board production. This article reviews the results of the Bombacopsis quinata breeding programme since 1988 and the conclusions that can be drawn.

The overall objective of the programme is to increase the productive capacities of the forests through genetic management and to bring about an increase in yield and quality.

Any breeding programme needs to address two basic questions: the first one is how to obtain a rapid increase in production of specified goods. This can be achieved by providing operational scale plantation programmes with improved planting materials derived from selected parent trees in an identified base population. The second aspect relates to the need to maintain a sufficiently broad genetic base to ensure sustainability of the programme in the long term. This will allow maintenance of a broad genetic base used for selection and breeding to improve the traits targeted by the breeding programme. In this regard it should be noted that no programme can be better than the genetic material on which it is based. No matter how much effort is put into selection and breeding, results will never be good if the base population is narrow or of poor genetic quality.

LOCATION

Monterrey Forestal land is located at 9º44' N and 74º50' W, at an altitude of between 50 and 250m above sea level, bordering Río Magdalena, the main waterway of Colombia, in the municipalities of Zambrano and Córdoba (Bol.), and at 9º49' N and 73º56' W, at an altitude of between 50 and 150 metres above sea level in the municipality of El Difícil de Ariguaní (Mag.). The area covers approximately 22 000 ha. Average annual rainfall varies between 700 and 1,600 mm, and soils are mainly vertisoils, to a lesser extent alfisoils, with pH of between 4.5 and 8.3.

BACKGROUND

In 1981, the company started large-scale reforestation with Pinus caribaea and a number of eucalypt species, including Eucalyptus camaldulensis. In the search for alternative species for commercial-scale reforestation, Monterrey Forestal began evaluating numerous native and introduced species in species trials; this is an ongoing activity. More than 50 species have been tested to date, and many of them have shown potential value and are therefore subject to further studies. Based on the trials, Monterrey Forestal has included in its planting programme the following species: Bombacopsis quinata, Gmelina arborea and, to a lesser extent, Sterculia apetala.

ADVANTAGES OF BOMBACOPSIS QUINATA

Bombacopsis quinata is a species which has a number of characteristics which facilitate its genetic improvement and its use in commercial plantations:

• Precocity of flowering, which enables seeds to be obtained in a short time (in some cases individuals start producing seeds at the age of one year), and thus to advance rapidly in the improvement programme.
• High survival, which facilitates the establishment of trials and commercial plantations.
• Resistance to drought, which enables planting even during a dry period.
• Easy to pollinate, which facilitates controlled crossing and the production of materials for the establishment of progeny trials.
• Regular and abundant seed production, which allows progeny trials to be established with less effort than for many other species.
• Self-incompatibility, which ensures that cross-pollinated flowers are not contaminated by selfed pollen.
• Orthodox seeds which can be stored for several years, which facilitates regular production of seedlings for planting and experimental work.
• Easy to propagate vegetatively, which allows cloning using relatively simple methods, for use in field trials, seed orchards and planting.

TREE IMPROVEMENT PROGRAMME

Selection of plus trees

The Bombacopsis quinata selection and breeding programme started in 1983 with the selection of 177 plus trees from natural forests and 62 plus trees in plantations along the Colombian Atlantic coast. A first generation clonal seed orchard was established using this material.

In addition to the above, 15 progeny/provenance trials have been carried out from 1987 to the present (including 438 families). Most of the material for the trials was supplied by CAMCORE². These trials enabled evaluation of provenances and progeny from the major part of the species' natural distribution in Central and South America (Colombia, Costa Rica, Honduras, Nicaragua and Venezuela).

Management of clonal seed orchards and seed production

The first company plantations were established using low quality seed that had been collected with no parental selection. But starting from the establishment of the first generation clonal seed orchard, research was carried out into the reproductive biology of the species (Urueña & Rodríguez, 1988), pollen management, artificial pollination, seed orchard management and seed handling (Kane, Urueña, Dvorak & Atehortúa, 1993), the latter with the aim of increasing seed production and germination rates.

Management of clonal seed orchards includes removing dry leaves from the orchard areas immediately following leaf shed, controlling insects that damage the flowers, collection of pollen, artificial pollination, harvesting and processing of seeds and their subsequent storage.

The following table shows seed production from the first and second generation clonal seed orchards.

Table 1: Seed production from clonal seed orchards (kg/year)

Given that one kilogram of seed contains approximately 37 500 seeds, 100 kg of Bombacopsis quinata seed will be enough to reforest 3 000 ha, with a spacing of 3x3 m.

In summary, from total dependence on unimproved commercial seed, Monterrey Forestal now has its own supply of improved seed and produces commercial surpluses for domestic and international use. Seed from the first generation clonal seed orchard was used in reforestation from 1988 on, and second-generation seed was used from 1991 on. In 1998 roguing was carried out in the second-generation clonal seed orchard, based on the results of progeny trials. In May 1999, the third generation clonal seed orchard was established.

Clonal banks

In order to conserve valuable genotypes for future use in the breeding programme, two clonal banks were established at Monterrey Forestal, in which most of the material used in the progeny trials, clonal seed orchards and provenance trials, was replicated.

PROGENY-PROVENANCE TRIALS

In the first stages of the Bombacopsis quinata breeding programme, open pollination progeny trials were used, which only enabled the maternal parent of each individual to be identified. With increased knowledge of floral biology of the species and the development of techniques for artificial pollination, it is now possible to carry out controlled crosses and thus to identify both parents of each sample.

Open pollinated trials enabled the estimation of General Combining Ability, thus allowing the roguing of clonal seed orchards in such a way that the best genotypes were left, independently of their phenotype. These trials also enabled the estimation of Additive Genetic Variation and heritabilities for the populations under study, but not non-additive genetic variability since only one parent was known. Open pollination in clonal seed orchards could also lead to back crossing, since the seeds from different mother trees may conceivably have a common pollen parent.

In the progeny trial established for the evaluation of second generation clonal seed orchard, partial diallel design was used with 10 groups of 6 clones plus three "controls" which enable results to be linked between the groups. Each group thus produced seed from 15 basic controlled crosses (plus three controls), that is, a total of 153 crosses.

Tree improvement

Forest tree improvement is the combination of forest genetics with silvicultural management techniques, such as site preparation or fertilization applied to improve productivity and the quality of products obtained from forests.

Tree improvement is only effective if it covers all genetic and forest management techniques available to the forester to obtain products as rapidly and as cost efficiently as possible.

It is of little importance how good the trees are from a genetic point of view if suitable silvicultural techniques are not employed since if inadequately managed they will be unable to express their genetic potential; likewise it matters little how good the silvicultural practices are if the reproductive materials used are of poor genetic quality.

In the case of Bombacopsis quinata, this meant that Monterrey Forestal had to improve knowledge of all aspects of managing the species, from the production and handling of seeds and plants in the nursery, to the management of plantations through their rotation.

Table 2 shows the number of trials linked to seed production and handling, the production of planting material and plantation management, from planting right through to harvesting, established by Monterrey Forestal over 15 years of research.

Table 2: Trials and research with Bombacopsis quinata, 1983-1998 at Monterrey Forestal.

Clonal programme

Vegetative propagation of Bombacopsis quinata is important if valuable genotypes tested at Monterrey Forestal are to be conserved, to multiply these genotypes, to establish clonal seed orchards, to evaluate these orchards and their interaction with the environment through clonal trials, and to capture the genetic gain in high yielding plantations. To date no clonal propagation programmes have been established by Monterrey Forestal for plantation establishment; nevertheless, experiments are planned.

RESULTS OF THE TREE IMPROVEMENT PROGRAMME

An improvement programme can target a number of characteristics, such as better adaptation to given sites, higher volume production and better wood quality, among others. The reduction of the rotation period and the increase in uniformity of harvested timber can also be considered major benefits. All these benefits are interrelated and cannot be assessed independently.

To date, no genotype-environment interaction has been observed for Bombacopsis quinata planted in the environmental conditions at Monterrey Forestal. This seems to indicate that the best individuals selected in one site will also perform well at any other site in the areas used.

Gains in volume production related to the combined effects of improved silvicultural methods and tree improvement in general exceed 300%, if the first plantations established on less suitable sites are compared with recent plantations on better sites.

It is estimated that gains obtained from using first generation clonal orchard seeds are approximately 25% in volume and those from rogued seed orchards lead to an additional 20 to 30% in volume growth. It is also estimated that utilization of second generation orchard seed could potentially generate a further 15% in growth. However, it should be noted that the final assessment of the actual gain from a breeding programme is determined by the financial profits.

It is estimated that Monterrey Forestal has invested close to $US 430 000 in the Bombacopsis quinata breeding programme over the past 15 years, in addition to investments made into research on silviculture. Taking into account that the company presently has approximately 3 000 ha of Bombacopsis quinata plantations and applying the total investment of the breeding programme into these plantations, without considering future plantations, $US 143 per hectare has been invested. An average increase of just 2 m_/ha in the plantations at the end of the rotation will be enough to justify the investments made.

Natural stands of Bombacopsis quinata have been to date over-exploited due to the high quality of the wood of the species. This is especially the case on the northern coast of Colombia, where virtually all non-planted stands and trees of commercial value have been cut during the last decades. Thanks to the intensive work carried out by Monterrey Forestal over the last 15 years, the species is the only native Colombian species currently benefiting from an advanced breeding programme, which also guarantees the species' conservation.

CONCLUSIONS

Regardless of species, the importance of tree improvement programmes for the sustainable production of wood is very high. These programmes should be linked to application in plantations and to research into silviculture and management, thereby allowing the high genetic quality of the improved individuals to be expressed fully.

The issue of conservation of genetic resources of a number of valuable forest tree species in Colombia should be addressed as soon as possible. Their genetic resources are being depleted and cut through selective unsustainable harvesting in natural forests. Through this process the best trees are selected, and in the best of cases only trees with poor stem form or defective individuals are left, rapidly reducing opportunities for seed collection and the use of the species in reforestation programmes, or for management of the natural stands. For species which flower only after many years of growth, a breeding and selection programme on the scale carried out for Bombacopsis quinata could very well require a long time to realize and taking care of our debt to nature is urgent.

It could be concluded that the major benefit of the breeding programme for Bombacopsis quinata is not only the gains to be realized by Monterrey Forestal. Thanks to this programme, the country has conserved genetic resources and has the opportunity to make good future use of the potential of one of the best commercial quality woods in it, even though the genetic resources of the species have been badly eroded over the recent decades.

BIBLIOGRAPHIC REFERENCES

Kane, M., Urueña, H., Dvorak, B. & Atehortúa, C. 1993. The potential of Bombacopsis quinata as a commercial species. In: Forest Ecology and Management Elsevier Science Publishers B.V. No. 56: 99-112.

Kane, M. & Urueña, H. 1991. Efecto de la densidad de siembra y el método cosecha de la producción de estacas de Bombacopsis quinata en el área de reproducción clonal. Zambrano, Bolívar, Colombia. Monterrey Forestal Ltda. Informe de Investigación No. 13. 11p.

Ladrach, W. 1993. Informe de consultoría. Raleigh, U.S.A. Zobel Forestry Associate. 68p.

Urueña, H. 1992. Production and management of Bombacopsis quinata (Bombacopsis quinata) seed. Trabajo presentado en: International Union of Forest Research Organization Conference. Cali, Colombia. 9 al 18 de octubre de 1992.

Urueña, H. 1991. Diferentes sistemas de polinización manual en Bombacopsis quinata. Zambrano, Bolívar, Colombia. Monterrey Forestal Ltda. Informe de Investigación No. 14. 3p.

Urueña, H. 1991. Siete años de manejo del huerto semillero clonal de Bombacopsis quinata de primera generación. Zambrano, Bolívar, Colombia. Monterrey Forestal Ltda. Informe de Investigación No. 10. 7p.

Urueña, H. & Rodríguez, M. 1988. Contribución al conocimiento de la biología reproductiva de Bombacopsis quinata (Jacq) Dugand (Malvales: Bombacaceae). Trianea No. 2 : 266-275.

Zobel, B. & Talbert, J. 1988. Técnicas de mejoramiento genético de árboles forestales. México, D.E. Limusa. 545p.

1. Received May 1999. Original in Spanish
2. The Central America and Mexico Coniferous Resources Cooperative (CAMCORE) based at the College of Forest Resources, North Carolina State University, USA