''Citrus australasica'', the Australian finger lime or caviar lime, is a thorny

understorey In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abo ...

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from tree ...

or small

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

of lowland subtropical

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

and rainforest in the coastal border region of

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , establishe ...

and

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

. It has edible fruits which are under development as a commercially sold crop.

Description

The plant is in height. The leaves are small, long and wide,

glabrous Glabrousness (from the Latin '' glaber'' meaning "bald", "hairless", "shaved", "smooth") is the technical term for a lack of hair, down, setae, trichomes or other such covering. A glabrous surface may be a natural characteristic of all or part of ...

, with a notched tip and

crenate A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

towards the apex.

Flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

are white with

petals Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usually ...

long. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...

is cylindrical, long, sometimes slightly curved, coming in different colours, including pink and green.

Cultivation and uses

History

Early settlers consumed the fruitLow, Tim, ''Wild Food Plants of Australia'', and retained the trees when clearing for agriculture. Colonial

botanists This is a list of botanists who have Wikipedia articles, in alphabetical order by surname. The List of botanists by author abbreviation is mostly a list of plant taxonomists because an author receives a standard abbreviation only when that auth ...

suggested that they should be cultivated, due to the lack of citrus alternatives.

Rising demand

The finger lime has been recently popularised as a gourmet

bushfood Bush tucker, also called bush food, is any food native to Australia and used as sustenance by Indigenous Australians, the Aboriginal and Torres Strait Islander peoples, but it can also describe any native flora or fauna used for culinary or ...

. The globular

juice vesicles The juice vesicles, also known as citrus kernels, (in aggregate, citrus pulp) of a citrus fruit are the membranous content of the fruit's endocarp. All fruits from the Citranae subtribe, subfamily Aurantioideae, and family Rutaceae have juice ves ...

(also known as pearls) have been likened to a "lime caviar", which can be used as a garnish or added to various recipes. The fresh vesicles have the effect of a burst of effervescent tangy flavour as they are chewed. The fruit juice is acidic and similar to that of a lime.

Marmalade Marmalade is a fruit preserve made from the juice and peel of citrus fruits boiled with sugar and water. The well-known version is made from bitter orange. It is also made from lemons, limes, grapefruits, mandarins, sweet oranges, bergamot ...

and

pickles Pickles may refer to: Dogs * Pickles (dog) (died 1967), a dog that found the stolen World Cup trophy in 1966 * Pickles (pickleball), a dog often cited as the name origin for the sport of pickleball * Mr. Pickles, the titular demonic dog in ...

are also made from finger lime. Finger lime peel can be dried and used as a flavouring

spice A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of plants used for flavoring or as a garnish. Spices a ...

. Commercial use of finger lime fruit started in the mid-1990s with

boutique A boutique () is a small shop that deals in fashionable clothing or accessories. The word is French for "shop", which derives ultimately from the Ancient Greek ἀποθήκη (''apothēkē'') "storehouse". The term ''boutique'' and also ''de ...

marmalades made from wild harvested fruit. By 2000 the finger lime was being sold in restaurants, and exported fresh. The finger lime has been recently grown on a commercial basis in Australia in response to high demand for the fruit. There is an increasing range of genetic selections which are budded onto

citrus rootstock Citrus rootstock are plants used as rootstock for citrus plants. A rootstock plant must be compatible for scion grafting, and resistant to common threats, such as drought, frost, and common citrus diseases. Principal rootstocks Five types of roots ...

. With the sudden high market demand for the fruit the primary source of genetic material for propagation has been selections from wild stock.

Diseases

In cultivation, the finger lime plant is grown in much the same way as other citrus species. It may be subject to some pests and diseases requiring pest control in cropping situations. This includes scale, caterpillars,

gall-wasp Gall wasps, also incorrectly called gallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this general ...

, and limb

dieback Dieback may refer to a number of plant problems and diseases including: * Forest dieback caused by acid rain, heavy metal pollution, or imported pathogens * The death of regions of a plant or similar organism caused by physical damage, such as from ...

. Fruit fly research has concluded that finger limes are a non-host plant to fruit flies and as such are not a quarantine risk to importing countries. Research conducted since the 1970s indicated that a wild selection of ''C. australasica'' was highly resistant to ''

Phytophthora citrophthora ''Phytophthora citrophthora'', also known as brown rot of citrus, is a soil borne oomycete that infects several economically important citrus crops. A diagnostic symptom of ''P. citrophthora'' is gummosis, wherein lesions around the base of the t ...

'' root disease, which has resulted in a cross-breeding program with finger lime to develop disease-resistant citrus

rootstock A rootstock is part of a plant, often an underground part, from which new above-ground growth can be produced. It could also be described as a stem with a well developed root system, to which a bud from another plant is grafted. It can refer to a ...

. In 2020, researchers began working with ''C. australasica'' to develop solutions for

Citrus greening disease Citrus greening disease (; or HLB) is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria, '' Liberibacter'' spp. The disease is vectored and transmitted by the Asian citrus psyllid, '' Diaphori ...

. The

CSIRO The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...

has also developed several ''Citrus'' hybrids by crossing the finger lime with standard ''Citrus'' species. These hybrids have created many

cultivars A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

which generate finger limes in many different colors ranging from light pink to deep blue-green. Finger lime is thought to have the widest range of color variation within any ''

Citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...

'' species. The color of the pulp (juice vesicles) comes in shades of green or pink including pale lime-green, pale pink, coral, and scarlet.

Taxonomy

Historically the finger lime was viewed as a member of the genus ''Citrus''. The Swingle system of taxonomy instead divided the historical true citrus into seven genera, placing the finger lime along with the round lime in a novel genus, '' Microcitrus''. However, subsequent studies have favored a broader concept of ''Citrus'' that reunites the genera separated by Swingle, restoring the finger lime to ''Citrus''.

References

External links

* * * {{taxonbar, from=Q141953 Australian Aboriginal bushcraft Australian cuisine Bushfood australasica Crops originating from Australia Edible fruits Flora of New South Wales Flora of Queensland australasica Plants described in 1858 Sapindales of Australia Taxa named by Ferdinand von Mueller