Genotypic and symbiotic diversity of native rhizobia nodulating red pea (Lathyrus cicera L.) in Tunisia

Nodulation and genetic diversity of native rhizobia nodulating Lathyrus cicera plants grown in 24 cultivated and marginal soils collected from northern and central Tunisia were studied. L. cicera plants were nodulated and showed the presence of native rhizobia in 21 soils. A total of 196 bacterial strains were selected and three different ribotypes were revealed after PCR-RFLP analysis. The sequence analysis of the rrs and two housekeeping genes (recA and thrC) from 36 representative isolates identified Rhizobium iaguerreae as the dominant (53%) rhizobia nodulating L. cicera. To the best of our knowledge, this is the first time that this species has been reported among wild populations of the rhizobia-nodulating Lathyrus genus. Twenty-five percent of the isolates were identified as R. leguminosarum and isolates LSI 1.5, LSI 1.7 and LS8.8 clustered with Ensifer meliloti. Interestingly, five isolates (LS20.3, LSI 8.3, LSI 9.10, LSI.2 and LS21.20) were segregated from R. iaguerreae and clustered as a separate Glade. These isolates possibly belong to new species. According to nodC and nodA phylogeny, strains of R. iaguerreae and R. leguminosarum harbored the symbiotic genes of symbiovar viciae and clustered in three different Glades showing heterogeneity within the symbiovar. Strains of E. meliloti harbored symbiotic genes of Clade V and induced inefficient nodules. (C) 2019 Elsevier GmbH. All rights reserved.