Résumé:
Nodulating chickpea bacteria were examined for their diversity and biogeography taking three winter
varieties into account as host plants. The study included nine sites in eastern Algeria with different
climates and physicochemical characteristics. In order to operate these sites, the most efficient
nodulation partners from these regions are sought after. Bacterial isolations were performed using
trapping protocols in greenhouse with each varieties and soil samples from each site. A molecular
study was carried out on the analysis of the sequences of five DNA fragments (DNA r16S, recA, IGS
16S-23S, nodC and nifH), showed that the nodules were occupied by rhizobia and non rhizobia, with a
high degree of diversity within each.
Four genera of rhizobia are present: Ensifer (46%), Rhizobium / Agrobacterium (23%),
Mesorhizobium (21%) and Burkholderia (10%). Large differences are noted between sites and
varieties for their ability to induce nodules and to involve a specific rhizobial genus or species as a
symbiot. Specificity is detected between the genera of Mesorhizobium and Burkholderia associated
with the site of Jijel as well as between the genus Ensifer and Biskra and between the genus Rhizobium
and Tebessa. With this latter pair, variety II resulted in the greatest nodulation level while the
nodulation efficiency of variety III is much more striking with the three other genera. Despite these
variations, no correlation was found between the chemical and physical characterizations of the soil
samples and those of the plant genotype.
Within the Mesorhizobium genus, at least 5 different known genospecies are present (M.ciceri, M.
amorphae, M. gobiense, M. opportunistum and M. Tamayadense), whereas some isolates could
probably represent at least one new species of Mesorhizobium, closely related to the M.ciceri / M.loti
cluster. Conversely to the significant genetic diversity shown by 16S rDNA, IGS 16S-23S and recA,
symbiotic diversity represented by nodC and nifH was low. This may reflect acquisition of the
symbiotic genes by lateral transfer.
To our knowledge, this study is the first systematic evaluation of chickpea rhizobia in Algeria. For the
first time it is shown that the species M. gobiense and M. tamadayense are symbiotic bacteria of
chickpea. Also for the first time it is revealed that the genus Mesorhizobium is not dominant and the
nodulation of chickpea is not limited to the genus Mesorhizobium and can be carried out by different
species and genera of rhizobia, although it should be confirmed by more studies. This certainly opens
up a broad spectrum for the selection of reliable symbiotic partners for the cultivation and yield of
chickpea in Algeria.
