Improved seeds result in higher yields, good stem form, and/or resistance to identified pests and diseases. Still, most tree seeds planted in the Asia-Pacific region are collected from unclassified seed sources, and usually give variable performance and poor yields.
Some improvement in seed quality can be gained merely by collecting seeds from selected stands outside the species' natural range. For meeting
current local demand for seeds, seed stands can he established in existing mature plantations by removing inferior phenotypes, controlling weeds, and applying fertilizer. Thinning stimulates the remaining trees to have large, healthy crowns for producing large seed crops. Isolating the stand from undesirable pollen sources can be difficult, but is desirable for better quality seed. Such improved stands can be classified as seed production areas.
Many existing plantations in the region have no registration of seed origin, and commonly have a narrow genetic base. To correct this for future seed demand, new seed production areas should be established using more seedlots from superior provenances. A new seed production area should be kept from outcrossing with outside pollen by completely surrounding it with an isolation zone or pollen dilution zone, and silvicultural treatments should begin at an early age. A seed production area thus established can provide better-quality seed than stands selected from existing plantations.
Three A. mangium seed production areas have been established in north Queensland. Australia using uaselected individual-family seedlots from natural stands (Harwood et al. in press). Highly significant between-family differences have appeared, although family rankings were stable over the two FNQ sites. Stem form was generally poor, possibly due to intensive site preparation. Nonetheless, some genetic improvement over seed from natural stands may be anticipated for two reasons; reduced inbreeding, and removal of inferior phenotypes by selective thinning. The authors also noted that an initial spacing of 5 x 2 m would appear to be better for A. mangium than the 3 x 1.8 m spacing used at these sites.
The seed orchard approach is the standard method of producing genetically improved seed in operational quantities (Andersson I960, cited by Zobel and Talbert 1984). Feilberg and Soegaard (1975) define seed orchard as a plantation of selected clones or progenies that is isolated or managed to minimize pollination from outside sources, and managed to produce frequent, abundant, and easily harvested crops of seed. Generally in Asia, the germplasm, budget, and qualified staff required for continuous and progressive seed orchard work are not available. Where this is the case, the ultimate goal of an intensive breeding program cannot be reached.
A few A. mangium seed orchards have been established in Australia (Harwood et al. in press). Indonesia (Wong in press; Suhaendi in press), Malaysia (Sim 1992), the Philippines (Pettersson and Havmoller 1984), Taiwan (Republic of China)(Pan, pers. comm.), and Thailand (Bhumibhamon and Atipanumpai 1992). Most of these are first-generation seed orchards from which high-quality seeds cannot be obtained easily. Often, pollinaiion among clones or families in the seed orchard are not well synchronized.
The seedling seed orchard has been the most commonly established type in the past decade or so. Sabah Softwoods Sdn. Bhd. (SSSB) pioneered in this, starting theirs in 1980 (Sim 1984). Other early seed orchards of this type were established by Swedish Match in the Philippines (Pettersson and Havmoller 1984) and PT lndah Kiat Pulp and Paper Corporation in Indonesia (Wong in press). With more intensive breeding underway and increasing use of vegetative propagation, clonal seed orchards are also being established. For example, SSSB has established bi-elonal seed orchards using selected and improved A mangium and A. imriculiformis to produce naturally crossed hybrid seeds (Chia in press).
In Thailand, a seed orchard consisting of 20 selected, open-pollinated families (15 from Australia, 4 from PNCi, and 1 from a plantation in the Philippines) has been established in Chachoengsao Province under a joint program by Thai Plywood Company and the Faculty of Forestry, Kasetsart University (Bhumibhamon and Atipanumpai 1992). The families have shown significant differences in height, diameter, crown growth, and (lower production. Flowering occurred at only 28 months. The families from PNG were the most prolific flower producers. The narrow-sense heritability values obtained were quite high, indicating that the characteristics were strongly inherited and significant gains can be expected from selection. Height growth had the lowest heritability (0.19). while flowering was the most strongly inherited characteristic (0.98).
For best results, a tree improvement program musí define a breeding plan and follow it. A comprehensive plan will review achievements, consider all resources. and specify objectives and options that provide lor:
choice of species and provenances acquisition of potentially useful genetic material
• vigorous implementation of interim, simple measures for early, local production of improved propagules estimation of genetic parameters specification of selection criteria: selection, breeding, and propagation methods; and a schedule of operations
• control of inbreeding, and maintenance of variation and a large effective population size
• monitoring of genetic technologies establishment of systems for data collection, management analysis and interpretation, and communication of results assignment of responsibilities development of a suitable administrative framework and enhancement of human resources, skills, and technologies (Nickles 1991)
A breeding plan must consider the resources available, the appropriate level of effort for each of these resources, and the relative importance of individual species being managed (Nickles 1985). Simple strategies are oitcn most appropriate. especially in the early stages of a breeding program, and where several species are involved (Barnes 1984; Griffin 1989). Flexibility is an important element of such a plan, which should be revised from time to time on the basis of increasing knowledge and experience.
Various breeding strategies for A. maiigium have been adopted in the Asia Pacific region, rellecting differences in available resources, program objectives, and stage of breeding. These plans range from simple strategies for mass production of A.mangium in Sabah (Monteuuis and Nasi 1992) to more integrated ones in the Philippines that include hybridization with A. duriculifomiis. A. crassicarpa, and A. leptoairpa (Pettersson and Havmoller 1984).
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