Stress tolerance, genetic analysis and symbiotic properties of root-nodulating bacteria isolated from Mediterranean leguminous shrubs in Central Spain

Abstract

Nine root-nodulating bacterial isolates were obtained from the leguminous shrubs Spartium junceum, Adenocarpus hispanicus, Cytisus purgans, Cytisus laburnuum, Retama sphaerocarpa and Colutea arborescens in areas of Central Spain. A poliphasic approach analyzing phenotypic, symbiotic and genetic properties was used to study their diversity and characterize them in relation to Mediterranean conditions. Stress tolerance assays revealed marked variations in salinity, extreme pH and cadmium tolerance compared with reference strains, with the majority showing salinity, alkalinity and Cd tolerance and three of them growing at acid pH. Variation within the 16S rRNA gene was examined by amplified 16S rDNA restriction analysis (ARDRA) and direct sequencing to show genetic diversity. Phylogeny confirmed the close relationship of four isolates with Bradyrhizobium canariense, three with Phylobacterium myrsinacearum, one with Rhizobium rhizogenes and another with Mesorhizobium huakuii. The cross inoculation tests revealed wide spectra of nodulation. This is the first report of P. myrsinacearum being able to nodulate these leguminous shrubs, and also the first time reported the association between B.canariense, R. rhizogenes and M. huakuii and C. laburnuum, C. purgans and C. arborescens, respectively. These results suggested that native rhizobia could be suitable candidates as biofertilizers and/or inoculants of leguminous shrubs with restoration or revegetation purposes in Mediterranean areas.

Preliminary characterization of slow growing rhizobial strains isolated from Retama monosperma (L.) Boiss. root nodules from Northwest coast of Algeria

“…Our results are in accordance with other previous investigations on the association between rhizobia and Retama from different Mediterranean areas (Spain, Algeria and Morocco); it has been noticed that Bradyrhizobium is the dominant genus of symbiotic nitrogen fixing bacteria associated with Retama species (Rodríguez-Echeverría et al, 2003Ruiz-Díez et al, 2009;Boulila et al, 2009;Guerrouj et al, 2013). The previous report on nodule isolates from R. raetam growing in arid areas of Tunisia yielded very contrasting results (Mahdhi et al, 2008).…”

“…It has been noticed that Bradyrhizobium is the dominant genus of symbiotic nitrogen-fixing bacteria associated with Retama species: Retama monosperma (L.) Boiss., Retamaraetam Webb and Berthel., Retama sphaerocarpa Boiss. (Rodríguez-Echeverría et al, 2003Ruiz-Díez et al, 2009;Boulila et al, 2009;Guerrouj et al, 2013). Recently, the novel B. retamae species, which groups with B. elkanii and B. pachyrhizi and related B. lablabi and B. jicamae type strains included in Bradyrhizobium group II ( Menna et al, 2009), has been isolated from R. sphaerocarpa and R. monosperma in Morocco and Spain (Guerrouj et al, 2013).…”

Biodiversity of rhizobia associated with cowpea cultivars in soils of the lower half of the São Francisco River Valley

“…The groups formed had between 26 % (group D) and 48 % (group C) of similarity. Genetic differences between rhizobium isolates using ARDRA were also observed by Han et al (2008), Stocco et al (2008), Ruiz-Díez et al (2009) and Sui et al (2009).…”

Symbiotic and Phenotypic Characteristics of Rhizobia Nodulaing Cowpea (Vigna Unguiculata L. Walp) Grown in Arid Region of Libya (Fezzan)

“…Tolerance to alkaline pH could be related to the calcareous and dry soils from which these isolates were isolated. However, some investigators found no correlation between the pH of the soil from which the organism was isolated and it is tolerant to different levels of pH in growth medium [43]. Bradyrhizobium strains native to tropical soils, grow at different pH levels and optimal growth occurs at pH 6.0, indicating that they are adapted to slightly acidic conditions [44].…”