Exploring rhizobia in wild native legumes in Belgium

Rhizobia are symbiotic bacteria capable of establishing root or stem nodules on various leguminous plants. An increasing number of nodule-forming bacteria have been reported, including bacteria from the alpha-, beta- and gammaproteobacteria (Chen et al., 2001; Chen et al., 2003; de Lajudie et al., 1994; de Lajudie et al., 1998; Jarvis et al., 1997; Jordan, 1982; Moulin et al., 2001; Rivas et al., 2002; Zakhia & de Lajudie, 2001). In Western Europe, relatively few native legume species have been studied in detail and therefore potentially a large part of the legume symbiont diversity remains to be discovered. In Belgium, legumes belong to 30 genera and comprise 113 plant species. They vary from annual and perennial herbs to shrubs and trees. In the present work, the diversity of bacteria isolated from root nodules from legumes in the area around Brakel (Belgium) was investigated. The sampling area comprised different habitat types, from nature reserves to industrial areas. Human activities are responsible for pollution and have a great influence on the plants. For example, in the more industrial habitats several times a year the area is sprayed with herbicides, such as Round up and Biofix. The aim was to get a first insight in the diversity present in these wild Belgian leguminous plants and to compare the diversity in the different habitats and plants. A total of 439 samples were taken covering 28 different plant species. We used the rep-PCR technique as a first screening to reduce the number of isolates, and 16S rDNA partial gene sequencing as an initial identification tool. To gain insights in the nodulation, fixation capacity and host range of the strains, NodC and NifH are being sequenced. Until now 71 rep-cluster were found in the analyzed samples and 23 clusters were identified. The preliminary data reveal the presence of Rhizobium and Sinorhizobium species in most of the samples but further analysis concerning the identification of the strains is still in progress