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Papers by Elektra Grant

Urban Forestry & Urban Greening, 2017

Abstract Koalas are iconic Australian tree-dwelling marsupials that are classified as vulnerable ... more Abstract Koalas are iconic Australian tree-dwelling marsupials that are classified as vulnerable because of threatening processes that include urban development, habitat fragmentation and inbreeding. Koalas eat the leaves of specific eucalypt trees but urban planners and landowners often prefer to plant smaller trees that pose less risk from falling limbs. We have conducted a long-term project to develop shorter koala-food trees for planting in parklands, schools, streets and gardens. We identified a little-known and geographically-confined species, Eucalyptus kabiana , that had potential for urban plantings. We assessed the height of E. kabiana trees in cultivation, determined whether their foliage was palatable to koalas, and compared the amenability to vegetative propagation of E. kabiana with that of an extensively-propagated related species, E. tereticornis . Cultivated E. kabiana trees were short, reaching around 3–5 m height after 6 years. Their foliage was highly palatable to koalas, and their cuttings proved to be amenable to propagation. Average rooting percentages for E. kabiana cuttings were 31–46%, similar to values obtained with E. tereticornis cuttings. Over 600 E. kabiana trees have thus far been distributed for planting in wildlife corridors, parklands, schools and gardens. The planting of more koala-food trees will help to alleviate the risks of inbreeding faced by koala populations in fragmented urban landscapes. School plantings also provide opportunities for students to learn about and interact with organisms such as koalas that inhabit the Eucalyptus trees.

Acta Horticulturae, 2016

Indigenous nut crops have great potential to improve the livelihood of rural populations in devel... more Indigenous nut crops have great potential to improve the livelihood of rural populations in developing countries. Canarium indicum (Burseraceae) is an indigenous species of the lowlands of Pacific Islands with great potential for developing a commercial nut industry. We examined a plantation of 50 families of six-year-old Canarium indicum trees to determine whether some families displayed early fruiting and desirable nut characteristics. One thousand seedlings from 50 known parent trees (20 seedlings for each parent) were planted in 2005. Trees were assessed in 2011 for early flowering and fruiting. Of the 693 trees surviving after six years, 189 trees were flowering and 155 trees bore fruit. Nuts were sampled from 25 trees to assess nut-in-shell and kernel weights. There were significant differences in mean nut-in-shell weight between trees. Nut-in-shell from the best selections weighed nearly twice as much as those from the poorest selections. Similarly kernel weights for the best selections were more than twice the weight of those from the poorest selections. However, the best selections for nut-in-shell weight were not the same as the best selections for kernel weight, highlighting the importance of assessing a range of characteristics. The highest mean kernel-recovery (kernel to nut-in-shell weight ratio) for the best tree was nearly twice that of the tree with the lowest kernel-recovery. These results highlight the benefits of early evaluation programs to identify superior selections that will increase yield and quality of Canarium indicum kernels in Pacific Island countries.

Nuts have huge potential to improve the livelihood of the rural poor in developing countries and ... more Nuts have huge potential to improve the livelihood of the rural poor in developing countries and meet the Millennium Development Goal to eradicate extreme poverty and hunger. Nuts often have a high protein and oil content, giving them excellent nutritional value. They can be processed and stored for long periods and therefore can improve food security, be sold for cash or be processed and exported to distant markets, thus helping the rural poor to participate in the cash economy. We report here on three processing systems for Canarium indicum nuts developed in three Pacific Island countries: Papua New Guinea, Solomon Islands and Vanuatu. Centralized processing has been developed in Papua New Guinea and fruit is purchased from smallholders at a central processing facility. The fruit is depulped, the nut-in-shell is cracked, the testa is removed and the kernel is dried using ovens in this facility. This provides a very high quality product and reduces the risk of microbial contaminati...

Industrial Crops and Products

Floral and reproductive biology of the medicinally significant rainforest tree, Fontainea picrosperma (Euphorbiaceae), 2017

A B S T R A C T Fontainea picrosperma (Euphorbiaceae) is a dioecious rainforest tree from norther... more A B S T R A C T Fontainea picrosperma (Euphorbiaceae) is a dioecious rainforest tree from northern Australia that is of commercial interest following the recent discovery of the putative anti-cancer agent, tigilanol tiglate, in its seed. Production of tigilanol tiglate will rely on purification from harvested fruit and therefore an understanding of the reproductive characteristics that determine fruit set of this species is critical. Most rainforest plant species rely exclusively on animal vectors to transport pollen between plants for successful reproduction. Flower traits and phenology can facilitate sexual reproduction by attracting pollinators whereas failure to attract pollinators can result in low fruit set due to pollen limitation. Here, we describe the floral morphology, flowering phenology and reproductive biology of F. picrosperma. This species bears small, white, actinomorphic flowers with a shallow receptacle. These floral traits are often associated with generalist insect pollination and are common to other dioecious tropical rainforest flowers. Individual female flowers persisted on the tree for several days longer than individual male flowers. Male panicles contained significantly more flowers than female inflorescences, and male flowers opened sequentially on a panicle whereas female flowers opened almost simultaneously within an inflorescence. F. picrosperma was pollen limited, as hand pollinated female flowers produced almost double the final fruit set (39.6 ± 4.4%) of open pollinated flowers (21.3 ± 3.4%). Optimised production of tigilanol ti-glate may therefore rely on improving pollen flow from male to female trees.

Australian Journal of Botany, 2014

The Corymbia and Eucalyptus species eaten by koalas are generally large trees, but these are ofte... more The Corymbia and Eucalyptus species eaten by koalas are generally large trees, but these are often unpopular with urban landowners and councils because of the dangers of limbs falling from a great height. We aimed to develop shorter koala food and habitat trees for urban areas by heterografting tall eucalypt species onto rootstocks of shorter species and comparing their survival and growth with homografted trees and control ungrafted trees. In total, 12 of 14 interspecific scion/rootstock combinations were grafted successfully in the nursery but graft compatibility and field survival depended on taxonomic relatedness. The six interspecific combinations that had multiple surviving trees at 5 years after planting were all between species within the same taxonomic section or between a species and its own interspecific hybrid. Almost all trees died from grafts between species in different taxonomic sections. In most cases, the height of surviving interspecific grafted trees did not differ from control intraspecific grafted trees or from ungrafted trees of their scion species. Grafting elicited a 'thrive or not survive' response that diminished its usefulness for producing shorter trees. However, one combination, E. moluccana/E. behriana, had field survival of 40% and reduced height (4.0 m vs 9.9 m). These could be valuable habitat trees for koalas and other fauna in urban areas.

Grant et al. 2019 Short distance pollen dispersal by Elektra Grant

Urban Forestry & Urban Greening, 2017

Abstract Koalas are iconic Australian tree-dwelling marsupials that are classified as vulnerable ... more Abstract Koalas are iconic Australian tree-dwelling marsupials that are classified as vulnerable because of threatening processes that include urban development, habitat fragmentation and inbreeding. Koalas eat the leaves of specific eucalypt trees but urban planners and landowners often prefer to plant smaller trees that pose less risk from falling limbs. We have conducted a long-term project to develop shorter koala-food trees for planting in parklands, schools, streets and gardens. We identified a little-known and geographically-confined species, Eucalyptus kabiana , that had potential for urban plantings. We assessed the height of E. kabiana trees in cultivation, determined whether their foliage was palatable to koalas, and compared the amenability to vegetative propagation of E. kabiana with that of an extensively-propagated related species, E. tereticornis . Cultivated E. kabiana trees were short, reaching around 3–5 m height after 6 years. Their foliage was highly palatable to koalas, and their cuttings proved to be amenable to propagation. Average rooting percentages for E. kabiana cuttings were 31–46%, similar to values obtained with E. tereticornis cuttings. Over 600 E. kabiana trees have thus far been distributed for planting in wildlife corridors, parklands, schools and gardens. The planting of more koala-food trees will help to alleviate the risks of inbreeding faced by koala populations in fragmented urban landscapes. School plantings also provide opportunities for students to learn about and interact with organisms such as koalas that inhabit the Eucalyptus trees.

Acta Horticulturae, 2016

Indigenous nut crops have great potential to improve the livelihood of rural populations in devel... more Indigenous nut crops have great potential to improve the livelihood of rural populations in developing countries. Canarium indicum (Burseraceae) is an indigenous species of the lowlands of Pacific Islands with great potential for developing a commercial nut industry. We examined a plantation of 50 families of six-year-old Canarium indicum trees to determine whether some families displayed early fruiting and desirable nut characteristics. One thousand seedlings from 50 known parent trees (20 seedlings for each parent) were planted in 2005. Trees were assessed in 2011 for early flowering and fruiting. Of the 693 trees surviving after six years, 189 trees were flowering and 155 trees bore fruit. Nuts were sampled from 25 trees to assess nut-in-shell and kernel weights. There were significant differences in mean nut-in-shell weight between trees. Nut-in-shell from the best selections weighed nearly twice as much as those from the poorest selections. Similarly kernel weights for the best selections were more than twice the weight of those from the poorest selections. However, the best selections for nut-in-shell weight were not the same as the best selections for kernel weight, highlighting the importance of assessing a range of characteristics. The highest mean kernel-recovery (kernel to nut-in-shell weight ratio) for the best tree was nearly twice that of the tree with the lowest kernel-recovery. These results highlight the benefits of early evaluation programs to identify superior selections that will increase yield and quality of Canarium indicum kernels in Pacific Island countries.

Nuts have huge potential to improve the livelihood of the rural poor in developing countries and ... more Nuts have huge potential to improve the livelihood of the rural poor in developing countries and meet the Millennium Development Goal to eradicate extreme poverty and hunger. Nuts often have a high protein and oil content, giving them excellent nutritional value. They can be processed and stored for long periods and therefore can improve food security, be sold for cash or be processed and exported to distant markets, thus helping the rural poor to participate in the cash economy. We report here on three processing systems for Canarium indicum nuts developed in three Pacific Island countries: Papua New Guinea, Solomon Islands and Vanuatu. Centralized processing has been developed in Papua New Guinea and fruit is purchased from smallholders at a central processing facility. The fruit is depulped, the nut-in-shell is cracked, the testa is removed and the kernel is dried using ovens in this facility. This provides a very high quality product and reduces the risk of microbial contaminati...

Industrial Crops and Products

Floral and reproductive biology of the medicinally significant rainforest tree, Fontainea picrosperma (Euphorbiaceae), 2017

A B S T R A C T Fontainea picrosperma (Euphorbiaceae) is a dioecious rainforest tree from norther... more A B S T R A C T Fontainea picrosperma (Euphorbiaceae) is a dioecious rainforest tree from northern Australia that is of commercial interest following the recent discovery of the putative anti-cancer agent, tigilanol tiglate, in its seed. Production of tigilanol tiglate will rely on purification from harvested fruit and therefore an understanding of the reproductive characteristics that determine fruit set of this species is critical. Most rainforest plant species rely exclusively on animal vectors to transport pollen between plants for successful reproduction. Flower traits and phenology can facilitate sexual reproduction by attracting pollinators whereas failure to attract pollinators can result in low fruit set due to pollen limitation. Here, we describe the floral morphology, flowering phenology and reproductive biology of F. picrosperma. This species bears small, white, actinomorphic flowers with a shallow receptacle. These floral traits are often associated with generalist insect pollination and are common to other dioecious tropical rainforest flowers. Individual female flowers persisted on the tree for several days longer than individual male flowers. Male panicles contained significantly more flowers than female inflorescences, and male flowers opened sequentially on a panicle whereas female flowers opened almost simultaneously within an inflorescence. F. picrosperma was pollen limited, as hand pollinated female flowers produced almost double the final fruit set (39.6 ± 4.4%) of open pollinated flowers (21.3 ± 3.4%). Optimised production of tigilanol ti-glate may therefore rely on improving pollen flow from male to female trees.

Australian Journal of Botany, 2014

The Corymbia and Eucalyptus species eaten by koalas are generally large trees, but these are ofte... more The Corymbia and Eucalyptus species eaten by koalas are generally large trees, but these are often unpopular with urban landowners and councils because of the dangers of limbs falling from a great height. We aimed to develop shorter koala food and habitat trees for urban areas by heterografting tall eucalypt species onto rootstocks of shorter species and comparing their survival and growth with homografted trees and control ungrafted trees. In total, 12 of 14 interspecific scion/rootstock combinations were grafted successfully in the nursery but graft compatibility and field survival depended on taxonomic relatedness. The six interspecific combinations that had multiple surviving trees at 5 years after planting were all between species within the same taxonomic section or between a species and its own interspecific hybrid. Almost all trees died from grafts between species in different taxonomic sections. In most cases, the height of surviving interspecific grafted trees did not differ from control intraspecific grafted trees or from ungrafted trees of their scion species. Grafting elicited a 'thrive or not survive' response that diminished its usefulness for producing shorter trees. However, one combination, E. moluccana/E. behriana, had field survival of 40% and reduced height (4.0 m vs 9.9 m). These could be valuable habitat trees for koalas and other fauna in urban areas.