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Accueil du site → Doctorat → Pays-Bas → 2007 → Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel

Wageningen Universiteit (2007)

Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel

Ndiaye, M

Titre : Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel

Auteur : Ndiaye, M. 

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 2007

Résumé partiel
Cowpea ( Vignaunguiculata Walp.) is the most important pulse crop in theSahelwith nearly 12.5 million hectares per year and is a valuable source of protein for human and animal nutrition. The most limiting factors for crop growth in the Sahelian zone of West Africa are water and nutrient stress. The average cowpea yields in farmers’ fields are low (0.2-0.5 ton/ha) and charcoal rot causes on average a yield loss of 10%, which is equivalent to 30.000 tons cowpea - an estimated value of $146 million for Niger and Senegal alone.Disease resistant or tolerant cultivars of cowpea against M . phaseolina are the most efficient control measures but such cultivars are not yet available. Solarization, addition of organic matter, maintenance of high soil moisture, fumigation and use of biocontrol agents have shown to be potential methods for control of soilborne pathogens.The objectives of the thesis is : 1)to characterize cowpea isolates of Macrophomina phaseolina prevalent in the different cowpea cropping systems in Niger and Senegal with respect to culture characteristics and host range ; 2) to determine effects of rotation of cowpea with fonio and millet on M. phaseolina disease of cowpea, and production and survival of microsclerotia in soil ; 3) to study the effects of compost and a biocontrol agent on M. phaseolina and charcoal rot on cowpea ; 4) to study the effects of solarization alone or in combination with organic residues on M. phaseolina and charcoal rot on cowpea.

Macrophominaphaseolina causes heavy yield loss to cowpea ( Vignaunguiculata ) grown in different cropping systems in the Sahel region ofAfrica. It was not known if cropping systems could influence physiological, genetic and pathogenic characteristics of M. phaseolina isolates. This study therefore aimed to analyze the population structure of M . phaseolina associated with three cropping systems in theSahel. Isolates were collected from soil and infected tissues of different cropping systems in Senegal and Niger and their growth potential at different temperatures, their morphology on PDA medium, their virulence on three cowpea cultivars and sequence analysis of the ITS (internal transcribed spacer) region of the nuclear ribosomal DNA gene studied.Isolates of M. phaseolina differed to a limited extent in temperature optimum, genetic make-up, and pathogenicity to cereal crops. The grouping according to physiological and genetic traits did not coincide with that based on pathogenicity. However, for the first time, we showed some specialization in pathogenicity to cereal crops except fonio ( Digitaria exilis )) for isolates obtained from fields grown to millet next to cowpea.

Mots clés : macrophomina phaseolina / vigna unguiculata / cowpeas / plant diseases / plant pathogenic fungi / integrated pest management / cropping systems / composts / biological control / sahel / niger

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