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Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania to identify the timing of capsule development and abortion, as well as the effect of pollination type, female tree, site, fertilisation, flower physical attributes, flower density, irrigation and weather events on capsule set and overall reproductive success. Controlled pollinations (CP), mass supplementary pollinations (MSP), open pollinations (OP) and un-pollinated controls (UP) were carried out at two orchard sites (Cambridge and Ridgley). Ramets of the same genotype differing in flower density and irrigation treatment were also compared for capsule set under MSP in three other experiments. No capsules were set in the UP, and capsule set was significantly lower following CP than OP and MSP. The genotypes at the lower altitude Cambridge site had a higher level of capsule set than the same genotypes pollinated at the Ridgley site. The major period of capsule abortion occurred between 20 and 80 days after pollination, coinciding with the period of capsule growth. There was a positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree. Flower physical attributes were found to correlate with reproductive success. Increased flower density had a negative impact on capsule set, as did irrigation. There was no clear evidence that weather events affected the rate of capsule abortion over the study period. Given that capsule abortion occurred during a period of fruit growth, that capsules with the lowest number of fertilised ovules aborted first and there is an impact from flower density and irrigation level, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Flowering time in a base population trial of Eucalyptus globulus ssp. globulus was highly variable and under strong genetic control. Races from the east coast of Tasmania and the Furneaux Group flowered approximately 1 month earlier than races from Victoria and King Island. These racial differences in flowering time were inherited in an additive manner in interprovenance F, hybrids, whereas the flowering time of interspecific F, hybrids between E. nitens and E. globullus was more similar to the late-flowering E. nitens.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania to identify the timing of capsule development and abortion, as well as the effect of pollination type, female tree, site, fertilisation, flower physical attributes, flower density, irrigation and weather events on capsule set and overall reproductive success. Controlled pollinations (CP), mass supplementary pollinations (MSP), open pollinations (OP) and un-pollinated controls (UP) were carried out at two orchard sites (Cambridge and Ridgley). Ramets of the same genotype differing in flower density and irrigation treatment were also compared for capsule set under MSP in three other experiments. No capsules were set in the UP, and capsule set was significantly lower following CP than OP and MSP. The genotypes at the lower altitude Cambridge site had a higher level of capsule set than the same genotypes pollinated at the Ridgley site. The major period of capsule abortion occurred between 20 and 80 days after pollination, coinciding with the period of capsule growth. There was a positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree. Flower physical attributes were found to correlate with reproductive success. Increased flower density had a negative impact on capsule set, as did irrigation. There was no clear evidence that weather events affected the rate of capsule abortion over the study period. Given that capsule abortion occurred during a period of fruit growth, that capsules with the lowest number of fertilised ovules aborted first and there is an impact from flower density and irrigation level, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania to identify the timing of capsule development and abortion, as well as the effect of pollination type, female tree, site, fertilisation, flower physical attributes, flower density, irrigation and weather events on capsule set and overall reproductive success. Controlled pollinations (CP), mass supplementary pollinations (MSP), open pollinations (OP) and un-pollinated controls (UP) were carried out at two orchard sites (Cambridge and Ridgley). Ramets of the same genotype differing in flower density and irrigation treatment were also compared for capsule set under MSP in three other experiments. No capsules were set in the UP, and capsule set was significantly lower following CP than OP and MSP. The genotypes at the lower altitude Cambridge site had a higher level of capsule set than the same genotypes pollinated at the Ridgley site. The major period of capsule abortion occurred between 20 and 80 days after pollination, coinciding with the period of capsule growth. There was a positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree. Flower physical attributes were found to correlate with reproductive success. Increased flower density had a negative impact on capsule set, as did irrigation. There was no clear evidence that weather events affected the rate of capsule abortion over the study period. Given that capsule abortion occurred during a period of fruit growth, that capsules with the lowest number of fertilised ovules aborted first and there is an impact from flower density and irrigation level, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Eucalyptus globulus is the main eucalypt species grown in Australian plantations. The focus on seedling deployment systems, coupled with exploitation of large, open-pollinated base populations for breeding purposes over the last two decades, has required a detailed understanding of the reproductive biology of this species. We review our research on the reproductive biology of E. globulus, with a focus on it’s breeding system and advances made in seed production systems. While most improved seed is still obtained from open-pollinated seedling or grafted seed orchards, the development of the one-stop/single-visit pollination procedure has revolutionised the breeding and deployment of this species. The reduced costs of controlled pollination has meant full pedigree-control can now be maintained in large advanced generation breeding populations and E. globulus is one of the few eucalypt species where large-scale production of manually pollinated seed for family forestry is being undertaken.

Megastigmus spp. are tiny wasps (bodies 2.5- 6.5mm in length) from the hymenopteran family Torymidae that destroy the seed of forest trees (Elliott and deLittle 1984). Many studies have examined their destructive effect on seed production in conifers, such as: Pseudotsuga; Abies; Cedrus; Cupressus; Juniperus; Larix and Picea (Roques and Skrzypczynska 2003). In Australia, they have been reported to feed on the seed of at least seven eucalypt species. However, despite reports of losses both in openpollinated seed orchard and controlled crossed seed of Eucalyptus globulus extending over many years, little is known of the biology and taxonomy of these insect species, nor the extent of the decrease in seed production they cause. The only study available suggests that the female wasps lay their eggs in eucalypt flowers (Drake 1974). After hatching, each small larva tunnel down into the developing seeds and gradually consume the content of a seed. The larva goes through several instars and the pupa develops within the seed coat. Fully-grown adult wasps emerge from the seed coat through a circular exit hole, and then exit through the top or side of the capsule usually before it opens. In this study we quantified the percentage of seed damaged by Megastigmus spp. predation in 384 seedlots of Eucalyptus globulus and examined whether there was a genetic basis to differences in the levels of seed predation observed.

While clonal propagation is used to establish some plantations of Eucalyptus globulus in countries such as Chile and Portugal, the majority of plantations worldwide are established from seed (Tibbits et al. 1997; Griffin 2001). The genetically improved seed used in industrial plantations is usually derived from open pollinated seed orchards (seedling or grafted), but with the advent of single-visit (Williams et al. 1999) and one-stop (Harbard et al. 1999) pollination procedures an increasing component is now derived from large-scale controlled pollination programs producing elite polymix or full-sib families. Regardless of the system, seed production varies markedly between trees and in most cases the choice of female can strongly influence the profitability of seed production (Leal and Cotterill 1997). In addition, as E. globulus has a mixed mating system (Griffin et al. 1987; Eldridge et al. 1993) and selfing results in severe inbreeding depression for growth traits (Hardner and Potts 1995), outcrossing rate is a key factor. Outcrossing rate will affect the genetic quality of seeds obtained from seed orchards and whether predicted additive genetic gains will be realised. One of the main drivers of the outcrossing rate is the level of self-incompatibility of the female tree (Patterson et al. 2001), which varies widely in the species (Potts and Savva 1988; Pound et al. 2002a,b, 2003). This paper reports the results of two studies aimed at determining whether there is a genetic basis to variation in traits affecting sexual reproduction in E. globulus. The first study examined the genetic basis of variation in the quantity and quality of open pollinated seed from over 800 seed orchard trees of E. globulus. The second study examined the genetic basis of the large variation in self-incompatibility observed within the species.

In recent years, E. nitens growers in southern Australia have established substantial areas of plantation to produce sawlog- and veneer-quality timber in addition to pulpwood. Drying degrade, manifested as checking (radially-oriented cracks) brought about by excessive collapse (excessive shrinkage of timber caused by the buckling or flattening of cells), has been identified as a problem that may significantly reduce recovery of appearance-grade sawntimber from such plantations. Collapse occurs in the initial stages of timber drying as free water is removed from cell lumens. True shrinkage occurs later in the drying process as water is removed from cell walls (Raymond et al. in press). This study expands on work undertaken by Kube and Raymond (2001) and Raymond et al. (in press) aimed at developing a suitable low-cost non-destructive technique to assess the propensity of an individual tree’s timber to collapse upon drying. It investigates different methods of assessing total core shrinkage (i.e. true shrinkage plus collapse) in dried wood cores. Genetic parameters are presented for each method of total shrinkage assessment, DBH and basic density.

The growth of E. globulus and E. nitens pollen tubes in styles of E. globulus was examined in order to elucidate the site of the unilateral barrier to hybridisation. Pollen tubes of E. nitens failed to grow the full length of the larger E. globulus style. E. globulus pollen tubes grew an average of 1.4 mm per day for the first 4 days, compared with 0.8 mm per day for pollen tubes of E. nitens. From days 4 to 14, the growth of E. nitens pollen tubes slowed to an average of 0.2 mm per day and virtually no growth occurred after day 14. In contrast, E. globulus pollen tubes grew through the style and into the ovary between days 5 and 14. By day 28, at about the time of style abscission, E. nitens tubes had grown only 6 mm, well short of the full length of the E. globulus style (9-10 mm). A similar difference in growth was obtained in vitro where E. nitens pollen tubes were significantly shorter than those of E. globulus. A comparison also including E. ovata, E. urnigera and E. gunnii indicated a significant correlation between style length and in vitro pollen tube length. It is argued that the unilateral cross-incompatibility between E. globulus and E. nitens is due to a structural barrier arising from an inherent limit to pollen tube growth which is associated with pistil size.

Flowering time in a base population trial of Eucalyptus globulus ssp. globulus was highly variable and under strong genetic control. Races from the east coast of Tasmania and the Furneaux Group flowered approximately 1 month earlier than races from Victoria and King Island. These racial differences in flowering time were inherited in an additive manner in interprovenance F, hybrids, whereas the flowering time of interspecific F, hybrids between E. nitens and E. globullus was more similar to the late-flowering E. nitens.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania to identify the timing of capsule development and abortion, as well as the effect of pollination type, female tree, site, fertilisation, flower physical attributes, flower density, irrigation and weather events on capsule set and overall reproductive success. Controlled pollinations (CP), mass supplementary pollinations (MSP), open pollinations (OP) and un-pollinated controls (UP) were carried out at two orchard sites (Cambridge and Ridgley). Ramets of the same genotype differing in flower density and irrigation treatment were also compared for capsule set under MSP in three other experiments. No capsules were set in the UP, and capsule set was significantly lower following CP than OP and MSP. The genotypes at the lower altitude Cambridge site had a higher level of capsule set than the same genotypes pollinated at the Ridgley site. The major period of capsule abortion occurred between 20 and 80 days after pollination, coinciding with the period of capsule growth. There was a positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree. Flower physical attributes were found to correlate with reproductive success. Increased flower density had a negative impact on capsule set, as did irrigation. There was no clear evidence that weather events affected the rate of capsule abortion over the study period. Given that capsule abortion occurred during a period of fruit growth, that capsules with the lowest number of fertilised ovules aborted first and there is an impact from flower density and irrigation level, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania to identify the timing of capsule development and abortion, as well as the effect of pollination type, female tree, site, fertilisation, flower physical attributes, flower density, irrigation and weather events on capsule set and overall reproductive success. Controlled pollinations (CP), mass supplementary pollinations (MSP), open pollinations (OP) and un-pollinated controls (UP) were carried out at two orchard sites (Cambridge and Ridgley). Ramets of the same genotype differing in flower density and irrigation treatment were also compared for capsule set under MSP in three other experiments. No capsules were set in the UP, and capsule set was significantly lower following CP than OP and MSP. The genotypes at the lower altitude Cambridge site had a higher level of capsule set than the same genotypes pollinated at the Ridgley site. The major period of capsule abortion occurred between 20 and 80 days after pollination, coinciding with the period of capsule growth. There was a positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree. Flower physical attributes were found to correlate with reproductive success. Increased flower density had a negative impact on capsule set, as did irrigation. There was no clear evidence that weather events affected the rate of capsule abortion over the study period. Given that capsule abortion occurred during a period of fruit growth, that capsules with the lowest number of fertilised ovules aborted first and there is an impact from flower density and irrigation level, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.