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Plant endophytes

Team GenetSYM/ Pascal Ratet

 

In fields, legume nodules are not only hosting rhizobia but also non rhizobial endophytes. In some plants there are more non rhizobial endophytes in the symbiotic organ than rhizobia and there is some form of specificity of the nodule microbiome. This suggests a choice by the plant and/or a compatibility with the rhizobial partner. We would like to understand the role that Nod factor signaling and immunity play in the recognition of these non rhizobial endophytes. To study this question we have initiated the isolation of bacteria from Medicago nodules formed in presence of non-sterile soil.

Legume plants are beneficial to sustainable agriculture mainly because they do not request expensive and polluting nitrogen fertilizer for their growth. Other major crops like wheat, barley, maize require addition of these polluting fertilizers for growth. We would like to know if these crops are able to interact with nitrogen fixing microorganisms. N2 fixing endophytes are for example present in sugar cane.

We have isolated from organic grown wheat (ie field developing plants grown without synthetic fertilizers) root endophytes able to fix nitrogen in vitro. Several bacteria were isolated and the genome of one of them sequenced (unpublished). Preliminary experiments indicate a close association of one of these strains with the root. Further experiments will show if this bacteria can behave as an endophyte.