Functional diversity of rhizosphere microorganisms from different genotypes ofArabidopsis thaliana

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Abstract
Activity and functional diversity of rhizosphere bacterial communities and fungal composition were studied in order to assess the effects of different genotypes (N8035, N224 and N8637) of \ud Arabidopsis thaliana\ud on these communities growing in different soils. Genotype effect and soil effect were studied independently. Also, the interactions between both factors (genotypes and soils) were considered. The activity was determined by thymidine and leucine incorporation analysis, and Biolog ECO plates were used to study bacterial functional diversity. Additionally, fungi groups (genera and/or species) were studied in the different rhizospheres. Statistical differences on thymidine incorporation between plant genotypes were only found in two of the soils. In addition, functional diversity (measured by Shanonn-Weaver index), showed statistical differences only in soil 1 for line N8035 (line B) \ud vs\ud . the other lines. Redundancy analysis (RDA) performed with Biolog data indicated and important effect of soil type, but also an effect of genotype since line N8035 (line B) was separated from the other lines within each soil in the RDA ordination, in spite of genotypic differences between them were minimum. Furthermore, carboxylic acids and amino acids were found to be the Biolog plate substrates with more influence in samples ordination in the Redundancy Analysis (RDA). However, fungi seem to be less labile to plant selection than bacteria probably due to a lower turn-over time of fungi than bacteria coupled with the short phenology of \ud Arabidopsis\ud . In this paper, plant-soil-micro-organism relationships in the rhizosphere were studied, and the complex interactions between them were highlighted. More studies are necessary to go deep in these interactions and to be able to asses the impact of genetically modified plants