Backhousia myrtifolia

''Backhousia myrtifolia'' (commonly referred to as ''carrol, neverbreak, iron wood, grey myrtle'' or ''cinnamon myrtle'') is a small rainforest tree species which grows in subtropical rainforests of Eastern Australia. First discovered and subsequently used by the indigenous communities of Australia, this plant produces oils that have a cinnamon-like aroma, and display both anti-bacterial and anti-fungal properties. Therefore, it has potential applications as not only a spice in food preparation, but also in the medical field as a treatment option for microbial infection. ''Backhousia myrtifolia'' can grow up to 30 metres. The leaves are ovate or elliptic, 4–7 cm long, and the flowers star-shaped in appearance.

''Backhousia Myrtifolia'' is renowned for the snow-white colour of its flowers, a characteristic that makes it suitable not only as a domestic/commercial crop but also as an internationally exported product.Firrel, C. (2006). To intervene or Not to intervene? An Evaluation of Strategic Intervention and its Usefulness in the Development of a Value Chain Alliance for the Native Flower Industry. MPhil Thesis, School of Natural and Rural Systems Management, University of Queensland. However, the susceptibility of this plant to "post-harvest browning syndrome" (a disease resulting in leaf discolouration and wilting), threatens its potential as a crop plant.

Characteristics

''B. myrtifolia'' is a native Australian species that belongs to the Myrtaceae family. ''B. myrtifolia'' is a canopy species of plant (occupying high light environments) that form coppiced thick trunks, and tend to grow in warmer, temperate rainforest conditions. They are most often found in regions close to watering bodies, such as the Eastern coastal edges of Queensland, New South Wales and Victoria. Its most common locations include the South Coast of NSW in Bega, and off Fraser Island in Queensland. ''B.myrtifolia'' is an evergreen and has an average life-expectancy of between 80 and 100 years. These plants tend to bloom between late spring and early summer, producing ivory white starfish-shaped flowers with 5 individual sepals and capsule like fruiting bodies. Lastly, oil glands are visible as fine white dots throughout the leaf's structure and are responsible for the release of four major organic compounds: methyl eugenol, (E)-methyl isoeugenol, elemicin and (E)-isoelemicin which collectively produce the plant's distinct cinnamon-like aroma.

Discovery and early uses

''Backhousia myrtifolia'' was first documented and subsequently named after an English botanist James Backhouse (1794–1869), in his report on Australian landscape and wildlife titled ''A narrative of a visit to the Australian colonies''. James Backhouse was renowned not only for his publications in the field of botany, but also the friendships he formed with the indigenous Australians, whose land he was conducting research on. However, prior to this ''B. myrtifolia'' was used extensively by indigenous Australians as a spice in cooking, due to its unique aroma and widespread accessibility.

Common diseases and cultivation options

B. myrtifolia species is fast-growing (as measured by plant biomass, leaf area and leaf biomass per plant) under ideal conditions, which includes fertile soil, high irradiance levels and sufficient water supplies. Maximum growth is achieved in the presence of oxygen-rich air (minimal carbon or nitric oxide pollutants) as well as nutrient-abundant soil, rich in micro-organism and mineral diversity. In addition to this ''B.myrtifolia'' tolerates drought, periods of inundation and repeated root disturbance, meaning that they are capable of flourishing in areas that experience constant temperature, and weather fluctuations. Therefore, this plant is suitable for cultivation in both domestic and commercial Australian environments (gardens or on footpaths) in both tropical (higher rainfall) and coastal climates. In these urban settings ''Backhousia myrtifolia'' has an average life expectancy of 60 years, requiring very little maintenance, presuming it receives consistently high sunlight levels. This is ideal for domestic governments and councils, since it minimises the costs associated with plant watering, trimming and root clearance.

Post-harvest browning syndrome

However, despite these seemingly ideal properties for domestic cultivation, the species is particularly susceptible to a condition termed "post-harvest browning syndrome", which involves the discolouration, browning and wilting of the plant's stereotypically dark green leaves.Sommano, S., Joyce, D.C., Dinh, S.Q., D’Arcy, B. (2012). Infection by Alternaria alternata causes discoloration of Backhousia Myrtifolia foliage and flowers. The journal of Horticultural Science and Biotechnology, 87(1), 41-46.   This browning syndrome was first documented between July to September 2008, on a 4-year stock of ''B. myrtifolia'' plants located at the University of Queensland. The discolouration was visible initially as small black dots on the surface of the leaves, progressing later into larger brown stained regions.Sommano, S. (2011). Browning mechanism in Backhousia Mmrtifolia. PhD Thesis, School of Agriculture and Food Sciences, The University of Queensland. This condition affected, approximately 30% of the harvested plants, signifying it infects populations of {''B. myrtifolia'' randomly, in non-specific quantities.Ekman, J., Eyre, J., Joyce, D. (2008). Flowers by Sea: Improving market access for Australian wildflowers. Australian government: Rural Industries Research and Development Corporation.

Although research is still being conducted into its causes, "post-harvest browning syndrome" has been attributed to two primary factors:
* Fungal and/or bacterial infection
* Prolonged heat exposure and lack of temperature control

Infection of ''B. myrtifolia'' by the fungus Alternaria alternata was analysed and confirmed via Koch's postulates