| Panama disease: a renewed threat in Asia |
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| Monday, 20 de November de 2006 | |
Fusarium wilt of banana, the notorious Panama disease that wiped out the plantations of Gros Michel export banana and led to its replacement by resistant Cavendish bananas in the second half of the twentieth Century is back-and with a vengeance! A new version of Panama disease, dubbed Tropical Race 4, has been spreading through plantations of Cavendish bananas in Asia over recent years, reducing exports and raising the cost of production. The disease has been successively reported in Taiwan, the Northern Territory of Australia, Indonesia (including Papua, formerly known as Irian Jaya), Malaysia, the southern provinces of China and, most recently, in the Philippines, the number one exporter of Cavendish bananas in Asia. The disease also threatens the traditional varieties that small-scale banana growers depend on for their livelihoods.This time around, however, Bioversity and its partners are there to meet the threat. An urgent priority is to find out exactly where the different virulent forms of the disease are to be found. The designation of four races represents an oversimplification. In reality, there are numerous variants of the pathogen, the fungus Fusarium oxysporum f. sp. cubense (Foc). Scientists classify the variants into ‘vegetative compatibility groups’, VCGs, based on the ability of their hyphae to fuse and form stable heterokaryons (cells that contain two or more nuclei). Each VCG has its own characteristics in terms of aggressiveness and the varieties of banana that it attacks most readily. The Asia-Pacific research network, BAPNET, has teamed up with specialists from the Forestry and Agricultural Biotechnology Institute of South Africa (FABI), and The Queensland Department of Primary Industry and Fisheries (DPI&F), to train a team of plant pathologists from the threatened region to carry out surveys, identify infected plants, collect the fungi and identify the VCGs. Detailed characterization studies are carried out in South Africa and Australia, where regional and international reference collections of Foc isolates are established. Working together, the BAPNET partners will be able to steadily build up a more complete picture of the threat and where it’s coming from. But what’s to be done about the disease, once we know where it is? In June 2006, a project was launched - with support from the Australian Centre for International Agricultural Research (ACIAR), and in collaboration with the Indonesian Tropical Fruits Research Institute (ITFRI), the Indonesian Agency for Agricultural Quarantine, the National Agricultural Research Institute (NARI) and National Agriculture Quarantine and Inspection Authority of Papua New Guinea, and DPI&F - to evaluate options to manage the disease. Banana growers so far have few alternatives to a cumbersome ‘scorched earth’ policy in which infected plants are uprooted and the residues burned on the spot—often with the addition of half a tonne or more of rice hulls to increase the temperature sufficiently to kill the pathogen in the soil. And even this onerous procedure is not always effective. Often growers have no choice but to abandon an infected piece of land. Australian and Indonesian scientists have already been working together to look at alternatives, including biological control agents that can attack or compete with the fusarium pathogen in the soil. The project will allow a wider range of options to be tested on farmers’ fields and lessons to be drawn for how to manage the disease wherever it occurs. One option will be to try resistant somaclonal variants developed in Taiwan. The various local cultivars in the collections of ITFRI will also be evaluated for their resistance to the various VCGs found in Indonesia. Another concern is the threat to wild relatives of the banana and traditional cultivars, including the ‘edible diploids’ that are considered to be among the earliest domesticated plants and the parents of our modern cultivars. We will work with the Plant Quarantine Service of Papua New Guinea to begin surveillance for the disease and prepare to contain it, if it crosses the border from Indonesia. The threat of fusarium wilt to banana diversity will also be addressed through the Global Musa Conservation Strategy which seeks to improve the management of field collections and ensure that safety back-ups are held in tissue culture in the international collection. |
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