Thursday, 31 July 2014

Researchers rally round to save the 'Tree of Life' from sudden death

ACIAR's Dr Richard Markham describes researchers' efforts to conquer a mysterious disease destroying coconut trees in Papua New Guinea (PNG)...

The coconut has been called the 'Tree of Life' in recognition of the many products and services that it provides to support the lives and livelihoods of coastal and island people around the Tropics.  Traditionally, people have drunk the ‘water’ and eaten the flesh from coconuts as part of their staple diet; they have used the fronds to thatch their huts and the ‘wood’ for construction and utensils. Since time immemorial, groves of palms have protected coasts against erosion and shaded other crops and livestock against the tropical sun. Now, those iconic silhouettes of palms against a blue sky are being reduced to bare poles by an unfamiliar disease – Bogia coconut syndrome.

Trouble in paradise - trees at various stages of decline from Bogia coconut syndrome
Although copra and coconut oil, facing competition from other, cheaper-to-produce edible oils, are no longer the main source of wealth in the Pacific countries, in PNG almost one-third of households, some 1.5 million people, still depend on coconuts for a significant part of their food and income. There was thus a ripple of concern when rumours surfaced, several years ago, of a mystery disease killing coconut palms – and reportedly other crops – in a remote site in Bogia district on the north coast of PNG’s mainland, part-way between Madang and the border with Indonesian West Papua. Initial samples sent for molecular analysis indicated that a phytoplasma (a parasitic bacterium) similar to that causing Coconut lethal yellowing in Africa and the Caribbean was associated with the disease; however, the disease did not appear to be spreading, so there the matter rested for a while.
Trees of Life reduced to bare poles from Bogia coconut syndrome

More recently, in 2009-2010, an outbreak of the disease at Furan village, just outside the busy city of Madang, attracted a great deal more attention, with the fear that trade might now spread the disease rapidly along the coast and through the islands. The national quarantine authority, NAQIA, imposed a ban on the movement of agricultural commodities out of the area, and researchers from the Oil Palm Research Association (OPRA) and the Cocoa Coconut Institute Limited (CCIL), with support from ACIAR, launched a scoping study to investigate the cause of the disease.

Although reports of the disease affecting a range of staple food crops proved to be an exaggeration, the phytoplasma was found in Sago and Betel nut palms (with similar yellowing symptoms) – both of which are economically important species in PNG. Meanwhile, another research team found a similar phytoplasma in bananas (but occurring over a much wider area than the Bogia coconut syndrome outbreak). The phytoplasma has also been found in several sap-sucking insect species but the tests were not sensitive enough to show whether these had been merely feeding on infected palms or whether they were capable of actively spreading the disease.

Intense debate on how to save the coconut genebank
Last week, researchers from Australia (Charles Sturt University and University of Queensland) and PNG (CCIL, OPRA, NAQIA and the National Agricultural Research Institute – NARI) got together in Madang to launch a larger project, to delve more deeply into the mysteries of the disease.

They will need to prove that it really is the phytoplasma that is killing the palms, establish how it differs (if at all) from the organism killing bananas, and find out how the phytoplasma is spread. Once this knowledge is in place, it should be possible to work out more targeted measures to limit the spread of the disease and manage it within the outbreak areas.

The researchers also started to wrestle with an additional ‘crisis within a crisis’: the international coconut genebank for the South Pacific lies within the quarantine area and so can no longer serve its function of preserving and distributing the genetic resources of coconut, for PNG and the region. Researchers from CCIL and NARI are testing the palms to see whether the collection itself is still free of the disease. If it proves to be so, NAQIA will lift the quarantine restrictions enough for coconuts to be moved out of the danger area to a quarantine island, where the germinating seedlings will be tested again and, if still ‘clean’ can be used to establish a new genebank.

ACIAR and the Global Crop Diversity Trust are standing by to provide technical support and offer alternative solutions if necessary.

By Dr Richard Markham, manager of ACIAR's Horticulture and Pacific Crops research programs

More information:

For more information, refer to the final report of ACIAR's scoping study PC/2011/056 Identifying potential vectors of 'Bogia Coconut Syndrome' in Madang Province, Papua New Guinea, which will be published soon on the ACIAR website.

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