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Chemical control of fireblight in pear trees, apple trees and related ornamental species has been investigated. Streptomycin is effective but is not authorized in all the member states of the Community, and nonphytotoxic flumequine based products are effective but are not authorized in all countries. The disease's cycle of development throughout the year has now been described and the virulence of the different bacterial strains is currently being recorded. Software for local early warning is currently being developed and a classification of different varieties and their resistance to the disease has been drawn up.

More than 40000 pear seeds resulting from more than 80 controlled crosses carried out in France were inoculated and about 4000 tolerant young hybrids are now undergoing trials for field value in Angers. A breeding programme for pear trees has also begun in Italy. It should be possible to produce less sensitive variants or mutants of the best varieties (Williams, Passe Crassane, etc) using in virto biotechnology. The research into breeding which has been carried out thus provides European farmers with a good picture of the sensitivity of the varieties grown in European conditions. The field performance of varieties bred in the USA and Canada is also known and it is possible to anticipate the emergence of new hybrids which are well suited to the conditions created by the spread of the disease. The appearance of the disease in Greece and its virulence there show that it may take on epidemic proportions in arid Mediterranean regions. An annex should therefore be set up for the purpose of breeding varieties suited to the mild winter conditions on the Mediterranean coast.

Fireblight is a bacterial disease of apple, pear and other Maloideae, including a number of ornamentals, which is caused by Erwinia amylovora. Direct control, though difficult, can be achieved successully by cultural and chemical means depending on inoculum level, stage of development of the host plant and climate. In the longer term, a more stable and satisfactory solution could be provided by the use of resistantvarieties, well adapted to each country. Research is underway to achieve direct control through improved detection of the bacteria by means of a computerized warning system, new active ingredients for chemical control and creation of new resistant varieties of pear as well as testing for resistance of existing cultivars of apple, pear, quince and medlar.

Experimental plots have been established in Greece and France and a computerized advisory package has been put together for use in the Mediterranean area. Sensitivity tests to the bacteria have been carried out on 20 Nashi varieties and 10 cotoneaster varieties. Over 1000 pear hybrids have been planted out for similar tests. A collection of 50 bacteria stains of diverse geographical origin, but particularly from Europe, has been made with the idea of setting up a test on plant cells in suspension for proof of action of a specific induced toxin. The choice and preparation of antigens destined for the manufacture of specific monoclonal antibodies has also been accomplished.
Fire blight is a bacterial disease of apple, pear, and other Maloideae including a number of ornamentals, which is caused by Erwinia amylovora. This disease is in the process of invading the whole Europe (within EEC only Spain and Portugal are free of fire blight). The latest contaminated country was Italy (1990).

Direct control, thought difficult, can be successfully achieved (by cultural and chemical means) as soon as local conditions are carefully taken care of : this is true in particular for inoculum level, stage of development of the host plant, climate. On the long run, a stable satisfactory solution could be provided by the use of resistant varieties, well adapted to each country.

The project deals with these two aspects of the control : direct control (experimentation in mediterranean zone of a computerized warning system, improvement of the detection of the bacteria, new active ingredients for chemical control) and both creation of new (resistant) varieties (pear) as well as testing for resistance of already existing cultivars (apple, pear, quince, medlar, ...).


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Institut National de la Recherche Agronomique (INRA)
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Centre de Recherche d'Angers Rue Georges Moreil Beacouze
49070 Angers

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Participants (5)