Nodulation of Sulla flexuosa ecotypes by Rhizobium sullae symbiovar sullae (sv. Nov) in Northern Morocco

Abstract Sulla flexuosa is a protein-rich Mediterranean pastoral and forage legume that is widely used for animal feed. In this work, we analyzed the diversity of the plant as well as the phylogenetic affiliations of its microsymbiotes. To our knowledge, this is the first evaluation of Sulla natural ecotypes in Morocco. We found that the plant populations constitute two distinct ecotypes, related to their geographical origin in Northern Morocco. The phylogenetic analysis of the 16S rRNA gene sequences of two representative strains, KS6 and BG1, isolated from the root nodules of each Sulla flexuosa L. ecotype, showed that they were closely related to Rhizobium sullae IS 123T with a similarity of 99.78%. This result was confirmed by MLSA using atpD, recA and glnII housekeeping gene sequences. Indeed, the phylogenetic analysis of the tree genes concatenated sequences sowed that the strains have 98.60 to 98.67% of similarity with R. sullae IS 123T. Furthermore, the phylogenic analysis of the nodC and nifH symbiotic genes showed that the two ecotypes Sulla flexuosa are nodulated by the same symbiovar of Rhizobium, for which we suggest the name of sullae (sv. nov.). The two representative strains tolerate water stress but are very sensitive to salinity, and can’t grow at temperatures higher than 35°C.