A breeding strategy involving inbreeding followed by crossbreeding of inbreds requires that the p... more A breeding strategy involving inbreeding followed by crossbreeding of inbreds requires that the production of superior inbred lines must be possible, but crosses between lines should exhibit heterosis, inbreeding should not substantially delay reproduction, and early selection between ...
Pulping properties and fibre characteristics of wood from eight-year-old ramets of 6 diploid and ... more Pulping properties and fibre characteristics of wood from eight-year-old ramets of 6 diploid and 5 tetraploid clones of Acacia mangium grown in Vietnam are reported. Individual clones were represented by two or three ramets. While kraft pulp yield at kappa 20 was very similar for diploid and tetraploids clones, tetraploid clones produced pulp with significantly longer (883 μm) and wider (20.0 μm) fibres, compared to the diploid clones (683 μm and 15.6 μm). The tetraploid cell wall thickness was greater, resulting in a coarser pulp. Pulmac fibre strengths of the tetraploid were greater than those of the diploid, although their fibre bonding area was lower. The kraft pulp of the best of the tetraploid clones had higher bulk, porosity and tear strength at constant tensile than pulp from a mix of diploid clones and was similar in these traits to softwood pulp.
The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitud... more The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitude 10°–44°S). Over 90% of the forests and woodlands of Australia are dominated by eucalypts, whose growth characteristics have evolved in environments where water and nutrients are limiting and fire is a recurrent phenomenon (Turnbull and Boland, 1984). Adaptive physiological characteristics of the genus have recently been reviewed by Eldridge and Cromer (1987).
The progeny of 2 provenances of E. regnans and 1 of E. obliqua were compared with progeny of 4 na... more The progeny of 2 provenances of E. regnans and 1 of E. obliqua were compared with progeny of 4 natural populations whose bark characteristics were intermediate between the 2 species. Assessment to age 15 yr showed that seed from the intermediate ...
Paternity analysis can be used to estimate mean effective pollen dispersal (micro(d)) by sampling... more Paternity analysis can be used to estimate mean effective pollen dispersal (micro(d)) by sampling offspring from a mother plant and assaying each for a large number of allozyme loci. The male in the population with the highest likelihood of paternity, based entirely on the degree of genetic relationship with the offspring (transition probability) or combined with information on probability of mating with the mother plant, is inferred as the pollen parent. Computer simulations show that the mean distance between inferred males and mother plants (d) reliably estimates micro(d) in defined circumstances. If male mating success decreases with distance from the mother plant, paternity inference based entirely on transition probabilities results in d values that are upwardly biased, perhaps considerably. More reliable estimates can be obtained in this situation when prior information on the general form of the relationship between mating success and distance between mates (the distance function) is used, along with transition probabilities, to infer paternity. However, this procedure is valid only when the general form of the distance function can be reliably assumed. Computer simulations also show that the bootstrap method can be used to closely approximate the SE of .
The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitud... more The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitude 10°–44°S). Over 90% of the forests and woodlands of Australia are dominated by eucalypts, whose growth characteristics have evolved in environments where water and nutrients are limiting and fire is a recurrent phenomenon (Turnbull and Boland, 1984). Adaptive physiological characteristics of the genus have recently been reviewed by Eldridge and Cromer (1987).
Polyploid breeding offers the possibility of increased variability in the search for improved gro... more Polyploid breeding offers the possibility of increased variability in the search for improved growth, site adaptation and disease resistance in tropical acacias. A key focus of breeding in Vietnam has been the production and testing of vigorous triploid clones which are expected to have the added advantage of being sterile. Triploids obtained by manual crosses between diploid and tetraploid trees or by bulk screening of seedlings derived from open-pollinated seedlots were verified using flow cytometry. Thirteen clones are under field testing for growth rate, tree form and fertility. Six of these are now reproductively mature and flowered as prolifically as diploids. However no pollen germinated, either on agar or on their own stigmas under controlled pollination. Only one clone (X01—F1 hybrid of tetraploid A. mangium and diploid A. auriculiformis) produced open pollinated pods on 0.05% of hermaphrodite flowers and these contained an average of 1.3 filled seeds per pod, about one-fifth the number observed in diploids. Less than 25% of germinated progeny from this triploid clone survived at 3 months after sowing and survivors were severely stunted with arrested growth. Ploidy and genotype analysis revealed them to be predominantly aneuploids, ranging from hyperdiploid to hypotetraploid with 95% being selfs. We are confident that we can select triploid clones which will be effectively infertile if deployed in plantations and may be of particular value in situations where the normal prolific natural regeneration of tropical acacias is highly undesirable.
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, 1985
Pinus radiata D. Don was inbred to different degrees, commencing with a founder population of 8 c... more Pinus radiata D. Don was inbred to different degrees, commencing with a founder population of 8 clones. Yield of filled seed was determined for each mating type. Mean yields (%), relative to outcrossing, were: half-sib 102; full-sib 97; S1 43; S2 42. An epistatic model was developed to predict the empty seed yield following selfing, assuming that homozygosity for several recessive co-lethals is necessary to kill an embryo. Calculations were then extended to predict the yields following different degrees of inbreeding. The proposed model gave a better fit to present results, and to other published results of similar investigations, than did an alternative based on action of independent recessive lethals. Implications for breeding and seed production strategy are discussed.
A breeding strategy involving inbreeding followed by crossbreeding of inbreds requires that the p... more A breeding strategy involving inbreeding followed by crossbreeding of inbreds requires that the production of superior inbred lines must be possible, but crosses between lines should exhibit heterosis, inbreeding should not substantially delay reproduction, and early selection between ...
Pulping properties and fibre characteristics of wood from eight-year-old ramets of 6 diploid and ... more Pulping properties and fibre characteristics of wood from eight-year-old ramets of 6 diploid and 5 tetraploid clones of Acacia mangium grown in Vietnam are reported. Individual clones were represented by two or three ramets. While kraft pulp yield at kappa 20 was very similar for diploid and tetraploids clones, tetraploid clones produced pulp with significantly longer (883 μm) and wider (20.0 μm) fibres, compared to the diploid clones (683 μm and 15.6 μm). The tetraploid cell wall thickness was greater, resulting in a coarser pulp. Pulmac fibre strengths of the tetraploid were greater than those of the diploid, although their fibre bonding area was lower. The kraft pulp of the best of the tetraploid clones had higher bulk, porosity and tear strength at constant tensile than pulp from a mix of diploid clones and was similar in these traits to softwood pulp.
The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitud... more The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitude 10°–44°S). Over 90% of the forests and woodlands of Australia are dominated by eucalypts, whose growth characteristics have evolved in environments where water and nutrients are limiting and fire is a recurrent phenomenon (Turnbull and Boland, 1984). Adaptive physiological characteristics of the genus have recently been reviewed by Eldridge and Cromer (1987).
The progeny of 2 provenances of E. regnans and 1 of E. obliqua were compared with progeny of 4 na... more The progeny of 2 provenances of E. regnans and 1 of E. obliqua were compared with progeny of 4 natural populations whose bark characteristics were intermediate between the 2 species. Assessment to age 15 yr showed that seed from the intermediate ...
Paternity analysis can be used to estimate mean effective pollen dispersal (micro(d)) by sampling... more Paternity analysis can be used to estimate mean effective pollen dispersal (micro(d)) by sampling offspring from a mother plant and assaying each for a large number of allozyme loci. The male in the population with the highest likelihood of paternity, based entirely on the degree of genetic relationship with the offspring (transition probability) or combined with information on probability of mating with the mother plant, is inferred as the pollen parent. Computer simulations show that the mean distance between inferred males and mother plants (d) reliably estimates micro(d) in defined circumstances. If male mating success decreases with distance from the mother plant, paternity inference based entirely on transition probabilities results in d values that are upwardly biased, perhaps considerably. More reliable estimates can be obtained in this situation when prior information on the general form of the relationship between mating success and distance between mates (the distance function) is used, along with transition probabilities, to infer paternity. However, this procedure is valid only when the general form of the distance function can be reliably assumed. Computer simulations also show that the bootstrap method can be used to closely approximate the SE of .
The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitud... more The genus Eucalyptus contains about 500 species, all but two of which occur in Australia (latitude 10°–44°S). Over 90% of the forests and woodlands of Australia are dominated by eucalypts, whose growth characteristics have evolved in environments where water and nutrients are limiting and fire is a recurrent phenomenon (Turnbull and Boland, 1984). Adaptive physiological characteristics of the genus have recently been reviewed by Eldridge and Cromer (1987).
Polyploid breeding offers the possibility of increased variability in the search for improved gro... more Polyploid breeding offers the possibility of increased variability in the search for improved growth, site adaptation and disease resistance in tropical acacias. A key focus of breeding in Vietnam has been the production and testing of vigorous triploid clones which are expected to have the added advantage of being sterile. Triploids obtained by manual crosses between diploid and tetraploid trees or by bulk screening of seedlings derived from open-pollinated seedlots were verified using flow cytometry. Thirteen clones are under field testing for growth rate, tree form and fertility. Six of these are now reproductively mature and flowered as prolifically as diploids. However no pollen germinated, either on agar or on their own stigmas under controlled pollination. Only one clone (X01—F1 hybrid of tetraploid A. mangium and diploid A. auriculiformis) produced open pollinated pods on 0.05% of hermaphrodite flowers and these contained an average of 1.3 filled seeds per pod, about one-fifth the number observed in diploids. Less than 25% of germinated progeny from this triploid clone survived at 3 months after sowing and survivors were severely stunted with arrested growth. Ploidy and genotype analysis revealed them to be predominantly aneuploids, ranging from hyperdiploid to hypotetraploid with 95% being selfs. We are confident that we can select triploid clones which will be effectively infertile if deployed in plantations and may be of particular value in situations where the normal prolific natural regeneration of tropical acacias is highly undesirable.
TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik, 1985
Pinus radiata D. Don was inbred to different degrees, commencing with a founder population of 8 c... more Pinus radiata D. Don was inbred to different degrees, commencing with a founder population of 8 clones. Yield of filled seed was determined for each mating type. Mean yields (%), relative to outcrossing, were: half-sib 102; full-sib 97; S1 43; S2 42. An epistatic model was developed to predict the empty seed yield following selfing, assuming that homozygosity for several recessive co-lethals is necessary to kill an embryo. Calculations were then extended to predict the yields following different degrees of inbreeding. The proposed model gave a better fit to present results, and to other published results of similar investigations, than did an alternative based on action of independent recessive lethals. Implications for breeding and seed production strategy are discussed.
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