Cadot Valérie, Boulineau François, Guénard Michel, Olivier Valérie, Molinéro-Demilly Valérie.
2002. Setting up a resistance test to Alternaria dauci of carrot by inoculation in the open field, as part of registering varieties in the national french catalogue of vegetable species.
In : Journées Jean Chevaugeon : IVe rencontres de phytopathologie - mycologie du 13 au 17 mars 2002. [Résumés]. CIRAD-MIDEC, INRA, CNRS, SFP
Résumé : In order to reduce the use of pesticides on vegetables and to avoid problems of residues, breeders research more and more genetic resistant varieties to diseases. In the carrot, new varieties, tolerant to Alternaria dauci (Kühn) Groves & Skolko, causal agent of leaf blight, a widespread and very damaging disease, have been developed. Up to now, two different types of tests have been carried out: the first by natural infection in the field and the second by artificial infection in control conditions. But no test in the field, by artificial infection on leaves, have been yet developed. However, this type of test enables controlling inoculum and obtaining a real response to the disease, contrary to artificial tests in a greenhouse. This is why the GEVES*, the organisation responsible for registering new varieties to the National and European catalogues, decided to set up a resistance test to Alternaria dauci by inoculation in the open field, with two main aims: - verify the breeder's declaration of resistance, - introduce officially this disease resistance like a new character of distinction. During four years, from 1997 to 2000, the susceptibility of 13 carrot cultivars to infection by Alternaria dauci was evaluated in field trials, in GEVES of Brion, with a spraying inoculation method. A specific field plot design has to be conceived to enable an uniform repartition of the fungus. Inoculum production, with different isolates from seeds, was prepared by the SNES (National Seed Testing Station). Two inoculations were performed by spraying a suspension of spores on foliage: the first at the stage 5-6 leaves and the second two weeks later. The period of sowing and inoculation were also experimented, with a delayed sowing in 1998 compared to 1997,1999 and 2000. Likewise, 3 notations, based on visual notations of leaf blight, were tested. During these 4 years of experimentation, the artificial infection provoked symptoms of leaf blight, However, the comparison of results show a more severe and earlier attack in 1997, 1999 and 2000, with a start at the end of August than in 1998, beginning in october. This weaker attack in 1998 could be explained by a later sowing and inoculations one month later, leading to show that inoculations must not be made too late in summer because moisture is necessary for the development of the disease. Nethertheless, the analysis of variance pointed out significant statistical differences between varieties and enabled to define 3 classes of resistance: - the susceptible class with as reference cultivar: PRESTO. - the intermediary class with as references: NEMO. - The tolerant class with as references: BOLERO. The Kendall correlation test performed on these four years showed a good stability of response for the susceptible and tolerant classes but less for the intermediary class. About notations, it is important to do it at least 2 times, to follow the evolution and verify the correlation. The optimal period is about 5-7 weeks after the second inoculation. An earlier notation 3 weeks after inoculation is not always statistically significative. And in contrast, some problems can appear if the notation is too late in relation with new leaves growth. Since 2000, this test of resistance has been used like official methodology for the study of new applicants to the Catalogue. BOLERO tolerance has not been overcame by the new cultivars. *GEVES: Group for Testing and Control of Varieties and Seeds. (Texte intégral)
Mots-clés Agrovoc : Alternaria dauci, Daucus carota, résistance aux maladies, test biologique, expérimentation au champ
Classification Agris : H20 - Maladies des plantes
Auteurs et affiliations
- Cadot Valérie, GEVES (FRA)
- Boulineau François, GEVES (FRA)
- Guénard Michel, GEVES (FRA)
- Olivier Valérie, GEVES (FRA)
- Molinéro-Demilly Valérie, GEVES (FRA)
Autres liens de la publication
Source : Cirad - Agritrop (https://agritrop.cirad.fr/490768/)
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