Table 1. A. mangium provenances in the international provenance trials (Awang and Taylor 1993)
Sl. No. | Provenance location (CSIRO seedlot No.) | Provenance region | Lat. (ºS) | Long. (ºE) | Altitude (m) |
1 | Julatten (12990) | Queensland Cairns Region | 16 34 | 145 35 | 400 |
2 | Daintree (12991) | Queensland Cairns Region | 16 17 | 145 31 | 60 |
3 | Rex Range (12992) | Queensland Cairns Region | 16 30 | 145 32 | 30 |
4 | Claudie River (13229) | Far North Queensland | 12 44 | 143 13 | 60 |
5 | Mission Beach (13230) | Queensland Cairns Region | 17 53 | 146 06 | 5 |
6 | NW of Silkwood (13231) | Queensland Cairns Region | 17 42 | 145 57 | 40 |
7 | Cowley Beach (13232) | Queensland Cairns Region | 17 41 | 146 05 | 5 |
8 | NE Walshs Pyramid (13233) | Queensland Cairns Region | 17 06 | 145 48 | 20 |
9 | E of Cairns (13234) | Queensland Cairns Region | 17 02 | 145 48 | 20 |
10 | Mourilayan Bay (13235) | Queensland CairnsRegion | 17 35 | 146 05 | 20 |
11 | Kurrimine (13236) | Queensland Cairns Region | 17 46 | 146 05 | 10 |
12 | El Arish (13237) | Queensland Cairns Region | 17 50 | 146 01 | 20 |
13 | Mission Beach (13238) | Queensland Cairns Region | 17 56 | 146 02 | 70 |
14 | Tully (13239) | Queensland Cairns Region | 17 55 | 145 52 | 50 |
15 | Cardwell-Ellerbeck (13240) | Queensland Cairns Region | 18 14 | 145 50 | 60 |
16 | Broken Pole Creek (13241) | Queensland Cairns Region | 18 21 | 146 03 | 50 |
17 | Abergowrie S. F (13242) | Queensland Cairns Region | 18 26 | 146 01 | 60 |
18 | Daintree (13279) | Queensland Cairns Region | 16 17 | 145 31 | 60 |
19 | Morehead (13459) | Papua New Guinea | 8 45 | 141 25 | 30 |
20 | Oriomo River (13460) | Papua New Guinea | 8 50 | 143 08 | 10 |
21 | Cassowary Range (13534) | Queensland Cairns Region | 16 32 | 145 25 | 60 |
22 | Piru, Ceram (13621) | Ceram, Indonesia | 3 04 | 128 12 | 150 |
23 | Sidei (13622) | Irian Jaya, Indonesia | 0 46 | 133 34 | 30 |
24 | Mossman (13846) | Queensland Cairns Region | 16 31 | 145 24 | 60 |
Results of these trials were reported by Harwood and Williams (1992). Highly significant provenance differences in growth trait among experimental sites and provenance regions were observed. For example, growth was generally faster at near-equatorial trial sites with mean annual height increment around 3-4 m, and slower at sites further from the equator. Papua New Guinea provenances were consistently the best performers, closely followed by the Claudie River provenance from north Queensland. The slowest growing provenances were from the Maluku province of Indonesia and southern parts of the distribution in Queensland. Other studies have given similar results (Nguyen and Le 1996; Otsamo et al. 1996; Tuomela et al. 1996).
Though variation of wood density among provenances was not significant, the heartwood formation variation was significant among 5-year-old trees of 23 families from 7 seed sources (Bhumington et al. 1992). It is highly heritable trait by the narrow heritability (Awang and Bhumibhamon 1993).
Plus tree selection
Plus tree selection and progeny testing for selected materials has taken place in several countries where A. mangium is planted on a large scale. Generally, the characteristics considered for plus tree selection are superior height, good diameter at breast height, stem straightness, good branching habit, good self pruning ability, resistance to pest and diseases and wood properties (density).
Seed stands and seed orchards
Since establishment of provenance trials, these countries have started further comprehensive seed collections. For example, Australian and several South East Asian organizations are developing improved breeds from wide bases of the best provenances with low levels of genotype-by-environment interaction at the provenance level (Harwood 1996). A. mangium seed orchards have been established in Australia, India, Indonesia, Malaysia, the Philippines, Taiwan and Thailand (Varghese et al. 1999). Expected gain in seedling volume production in progeny from seed orchards of A. mangium in Indonesia is more than 50-70% compared to local seeds planted (Kurinobu and Nirsatmanto 1996). Because of asynchronous flowering among trees and families in seed orchard (Awang and Bhumibhamon 1993), the seed production of most of the first generation is low. In Fig. 5 the seed orchard in India is shown.
Fig. 5. Acacia mangium seed orchard at Nilambur, Kerala, India.
ТЬ build up a base for clonal forestry programme (Arisman and Havmoller 1994), A. mangium × A. auriculiformis experimental hybrid seed orchards have been established in Indonesia. Hybrid clones with outstanding growth and form selected and propagated by tissue culture are being tested in Vietnam (Le 1996). Vegetative propagation of the hybrid by striking cuttings from coppice shoots is being used in Bangladesh (Banik et al. 1995).
A breeding programme has been initiated by Institute of Forest Genetics and Tree Breeding, India (IFGTB) by obtaining seeds from established seedling seed orchards of Australia, Fiji and Indonesia as well as from identified natural provenances, and raising pedigreed as well as bulked seed orchards after culling inferior families (Varghese et al. 2001).
Seed Biology
Seed harvesting and collection
In India and Indonesia seeds are collected from plantations or orchards by locally hired climbers who cut off branches and strip the fruits into bags. After air drying, the pods are hand threshed and seeds are cleaned. Seeds can be produced from the 18 to 20-month-old trees, but the flowering and fruiting seasons are quite different based on the locations. In Indonesia fruits ripen in July, while in Papua New Guinea they ripen in September (Krisnawati et al. 2011).
Seed extraction and cleaning
Seeds can be extracted manually after sun-drying for several days (24-48 hours) until the pods turn brown/black and split. The drying temperature should remain below 43°C to avoid loss of seed viability (Krisnawati et al. 2011).
The pods should be processed as soon as possible after harvest. If pods and seeds are not thoroughly dried, the best storage during transport is cloth bags. Otherwise, the heat and humidity encourage the development of fungi. In India, seeds are extracted manually after sun drying for several days until the pods turning brown and/or black and split. Pods and seeds should not be left long to dry in the sun, as temperatures over 43°C can reduce viability. In Malaysia, pods are dried in a simple drying chamber equipped with an electric heater and a domestic fan (Adjers and Srivastava 1993). Seed moisture content should be reduced below 13% to prevent fungus development. Extraction with flailing thresher followed by winnowing as described in Doran et al. (1983) is suitable for this species. Because threshing of pods and seeds produces a highly irritating dust, workers need protection (Adjers and Srivastava 1993). In Fig. 6, fruits are shown.