A blog maintained by Tevita Kete, PGR Officer
Secretariat of the Pacific Community (SPC), Suva, Fiji Islands
This weblog documents the activities of Pacific Agricultural Genetic Resources Network (PAPGREN), along with other information on plant genetic resources (PGR) in the Pacific.
The myriad varieties found within cultivated plants are fundamental to the present and future productivity of agriculture. PAPGREN, which is coordinated by the Land Resources Division of the Secretariat of the Pacific Community (SPC), helps Pacific countries and territories to conserve their crop genetic diversity sustainably, with technical assistance from the Bioversity International (BI) and support from NZAID and ACIAR.
SPC also hosts the Centre of Pacific Crops and Trees (CEPaCT). The CEPaCT maintains regional in vitro collections of crops important to the Pacific and carries out research on tissue culture technology. The CEPaCT Adviser is Dr Mary Taylor (MaryT@spc.int), the CEPaCT Curator is Ms Valerie Tuia (ValerieT@spc.int).
PAPGREN coordination and support
Mr William Wigmore
Mr Adelino S. Lorens
Dr Lois Englberger
Mr Apisai Ucuboi
Dr Maurice Wong
Mr Tianeti Beenna Ioane
Mr Frederick Muller
Mr Herman Francisco
Ms Rosa Kambuou
Ms Laisene Samuelu
Mr Jimi Saelea
Mr Tony Jansen
Mr Finao Pole
Mr Frazer Bule Lehi
Interested in GIS?
Monday, July 25, 2005
Posted 4:24 PM by Luigi
Protecting kava from kava dieback disease
Dr Richard Davis, the SPC virologist will be interviewed for the "In the Loop" programme of Radio Australia. Below is the information he provided. Richard will be going on air at 12.40 Fiji time on Tuesday July 26.
Kava is a crop of enormous cultural and economic significance in the Pacific Islands. There is a huge potential export market for kava, which may immediately take off again, following the recent lifting of a ban on kava sales in Europe.
Kava dieback disease is a devastating problem. Affected plants develop a black soft rot, and ‘melt down’ rapidly. It spreads quickly and can destroy entire plantings.
It was first reported in Fiji in 1932. It then became the principal kava production constraint in the Pacific, especially in Fiji, Tonga, Samoa, and Vanuatu. In Fiji islands today, annual losses to kava dieback are estimated to average 40%.
In Fiji Islands, kava dieback reached serious national epidemic proportions in the late 1990s. This is because production intensity driven by high export prices, became very high. The threat today is that this story will be repeated if poorly planned rapid expansion of kava production occurs again.
The cause of kava dieback disease
The cause of kava dieback remained a deep mystery over decades of investigation until the early 1990s when an Australian (ACIAR) funded research project brought together workers from Tonga, Fiji, Vanuatu and Samoa. At last, progress was made: a plant infecting virus called Cucumber mosaic virus (CMV) was implicated. However, we know today that it is not such a simple story. Latest thinking is that dieback results from a complex of interactions of kava with environmental and other factors with CMV at its centre. Exactly what is involved probably varies in different places and at different times. However, one thing is crystal clear: take CMV out of the picture and you do not have dieback any more.
Tackling the problem
Controlling CMV is not easy. There is no ‘silver bullet’ answer for kava farmers. No suitable disease resistant varieties of kava have yet been found. There are no chemical sprays available which kill the virus in infected plants. Spraying to kill the insects which spread the disease from plant to plant does not give effective control either. All this is made worse by the fact that CMV is very common and can infect an extremely broad range of other plants.
Since the mid 1990s, no further research was undertaken on kava dieback until late 2002 when the Fijian Ministry of Agriculture, Sugar and Land Resettlement (MASLR) and the Secretariat of the Pacific Community (SPC) started work together. Funding was provided by the European Union’s Plant Protection in the Pacific (PPP) project, managed by SPC. As a first step, a major biotechnology upgrade at the Ministry’s Koronivia Research Station and at the University of the South Pacific was made.
Biotechnology, including the DNA analyses used in forensic police work, has now unlocked the door to understanding kava dieback. New breakthroughs have been made that provide the foundation for an integrated dieback disease management package. It will be based on a combination of simple actions growers can take that reduce the sources of the virus and suppress plant to plant spread - no pesticides involved, and all in an agroforestry context.
This package takes advantage of two principal weaknesses of CMV:
Details are now being finalised, but the package is basically:
Growers must only use uninfected planting material. In the short term, this can be achieved to some extent by very carefully advised selection from what is currently available in the field. In the longer term, virus tested kava planting material should be made available, hopefully by commercial tissue culturing.
If a kid has flu virus, the best thing to do is keep him or her out of the classroom, to prevent spread to the other kids. As plant diseases are like human ones, growers were first advised to destroy all diseased plants, before they infect their neighbours. This was never widely adopted because each plant is of high value and growers know that some new growth follows stem rot.
Kava is best intercropped in early stages of growth and planting non-hosts between kava plants will reduce within plot spread of CMV. Studies to determine which key kava intercrops and weeds are alternative hosts for the dieback causing strain(s) of CMV are progressing well and definitive advice for growers is imminent.
Dieback is much less of a problem when grown in the traditional way. That is in small and isolated plantings grown amongst natural vegetation and below a tree canopy. This is because many of these plants are not hosts to the disease. Because of this, they act as a buffer zone, protecting the kava from incoming insects carrying CMV. The more separated the plantings are from each other, the better this works.
Kava also seems to be less likely to develop dieback when CMV is around when it is growing vigorously. For this reason, growers should only plant in the right kinds of soils: well drained, fertile and high in organic matter.
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