Biotic changes in relation to local decrease in soil conduciveness to disease caused by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> |
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Authors: | Muhammad Anees Arne Tronsmo Véronique Edel-Hermann Nadine Gautheron Vincent Faloya Christian Steinberg |
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Institution: | 1.INRA-Université de Bourgogne, UMR 1229 Microbiologie du sol et de l’environnement - CMSE,INRA,Dijon,France;2.Department of chemistry, biotechnology and food science,Norwegian University of Life Sciences,Aas,Norway;3.Unité Expérimentale d’Epoisses, INRA,Bretenières,France |
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Abstract: | The relationships between biotic changes and local decrease in soil conduciveness in disease patches towards the disease incited
by Rhizoctonia solani AG 2-2 in a sugar beet field in France were investigated. Soil samples from healthy and diseased areas were analysed for
bacterial and fungal densities, molecular and physiological microbial community structures, and antagonistic abilities of
Trichoderma isolates collected from diseased and healthy areas. Although the inoculum density was higher inside the disease patches,
the respective soil was less conducive towards disease incited by R. solani AG 2-2. It was concluded that the pathogen was present in healthy areas but did not incite disease in field conditions. Conversely,
the response of the microflora to previous development of R. solani in diseased areas prevented further pathogenic activity. Indeed, genetic and physiological structures of the fungal communities
and physiological structures of the bacterial communities were modified in disease patches compared to healthy areas. The
terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that the peaks corresponding to R. solani and Trichoderma spp. were higher inside the patches than in the healthy areas. Trichoderma isolates from the disease patches were more antagonistic than those from the healthy areas. These results suggest that disease
caused by R. solani AG 2-2 induced changes in genetic and physiological structure of microbial populations and development of antagonists. The
decreased conduciveness inside the patches may help explain patch mobility in the following season. |
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