Diversité des rhizobia associés au genre Hippocrepis en Algérie

Abstract

La présente étude porte sur la nature des rhizobia associés aux légumineuses du genre Hippocrepis L. qui compte une dizaine d’espèces en Algérie et pour laquelle très peu de travaux ont été jusqu’ici consacrés. Les résultats de nos investigations qui ont portés sur 26 plants représentant 8 espèces de ce genre et provenant de 17 localités du nord et du sud du pays révèlent que tous les plants étaient nodulés et fixateurs d’azote, ce qui indique que les 8 espèces identifiées sont capables d’établir une symbiose efficiente avec les rhizobia présents dans les sols qui les supportent. Le séquençage du gène de l’ARN 16S des 26 souches de rhizobia isolées et authentifiées par des tests de nodulation au laboratoire, permet de les assigner à 16 espèces de rhizobia réparties sur 5 genres : Ensifer, Mesorhizobium, Bradyrhizobium, Rhizobium et Neorhizobium avec une prédominance des représentants des genres Ensifer et Mesorhizobium. Les résultats de cette étude qui est la première dédiée spécifiquement au genre Hippocrepis indiquent que la symbiose à rhizobia et la capacité d’utiliser, par ce biais, l’azote atmosphérique sont communes chez les représentants de ce genre en Algérie, ils révèlent aussi la grande diversité des rhizobia qui sont associés à ce genre.
 Abstract: The present study focuses on the nature of the rhizobia associated with legumes of the genus Hippocrepis L. which counts about ten species in Algeria and for which very little work has been performed so far. The results of our investigations, which focused on 26 plants representing 8 species of this genus and coming from 17 localities in the north and south of the country, show that all plants were nodulated and nitrogen-fixing, which indicates that the species identified are capable of establishing an efficient symbiosis with the rhizobia present in the soils that support them. The sequencing of the 16S RNA gene of the 26 strains of rhizobia isolated and authenticated by nodulation tests in the laboratory, allows their assignation to16 species of rhizobia spread over 5 genera: Ensifer, Mesorhizobium, Bradyrhizobium, Rhizobium and Neorhizobium with a predominance of representatives of the genera Ensifer and Mesorhizobium. The results of this study, which is the first dedicated to the genus Hippocrepis, show that the rhizobial symbiosis and its ability to use atmospheric nitrogen are common among representatives of the genus Hippocrepis in Algeria and reveal a great diversity of associated rhizobia

Phylogenetic diversity of the rhizobial nodulating symbionts associated to the introduced Vachellia karroo (Hayne) Banfi and Galasso (Fabaceae) in Algeria

“…In Algeria, research conducted by Djouadi et al [30] revealed a predominance of the Ensifer genus in nodules of Hippocrepis L. species from southern Algeria, while species belonging to the Bradyrhizomium genus colonize nodules of Hippocrepis species distributed in northern Algeria. Additionally, Amrani et al [5] demonstrated that plants of Acacia saligna cultivated in Algerian nurseries are rarely nodulated by species of the Bradyrhizobium.…”

“…The seeds were first surface-sterilized by immersion in 5% calcium hypochlorite solution for 10min, rinsed with sterile distilled water, and then were grown in perforated polyethylene bags (15x25 cm) filled with a mixture of nursery soil and river sand (v/v, 2/1). The used sand was previously sterilized by autoclaving at 121°C (1 hour at 121°C, three times spaced 24 hours apart over a period of three days) [30]. The irrigation was performed every three days with a volume of water equivalent to 100% of the soil's water holding capacity.…”

“…Suspensions were centrifuged for 5 min at 6000 g and then washed twice, pellets were re-suspended. DNA was extracted using the same protocol adapted in Djouadi et al [30].…”

“…The native and introduced Algerian floras, especially legumes as well as the accompanying rhizospheric bacteria, remain understudied despite the significant systematic, ecological and biogeographic diversity described since earlier works [26,4,27,5,28,29,30,31,32].…”