Phenotypic and genotypic diversity of root nodule bacteria from wild Lathyrus and Vicia species in Gaziantep, Turkey.

This study identified the phenotypic and genotypic characteristics of the bacteria that nodulate wild Lathyrus and Vicia species natural distribution in the Gaziantep province of Turkey. Principle component analysis of phenotypic features revealed that rhizobial isolates were highly resistant to stress factors such as high salt, pH and temperature. They were found to be highly sensitive to the concentrations (mg/mL) of the antibiotics neomycin 10, kanamycin, and tetracycline 5, as well as the heavy metals Ni 10, and Cu 10, and 5. As a result of REP-PCR analysis, it was determined that the rhizobial isolates were quite diverse, and 5 main groups and many subgroups being found. All of the isolates nodulating wild Vicia species were found to be related to Rhizobium sp., and these isolates were found to be in Clades II, III, IV, and V of the phylogenetic tree based on 16S rRNA. The isolates that nodulated wild Lathyrus species were in Clades I, II, IV, V, VI, VII, and VIII, and they were closely related to Rhizobium leguminasorum, Rhizobium sp., Phyllobacterium sp., Serratia sp., and Pseudomonas sp. According to the genetic analyses, the isolates could not be classified at the species level, the similarity ratio was low, they formed a distinct group that was supported by strong bootstrap values in the phylogenetic tree, and the differences discovered in the network analysis revealed the diversity among the isolates and gave important findings that these isolates may be new species.

Modification of Growth and Physiological Response of Coastal Dune Species Anthyllis maritima to Sand Burial by Rhizobial Symbiosis and Salinity.

The aim of the present study was to establish an experimental system in controlled conditions to study the physiological effect of abiotic/biotic interaction using a rare wild leguminous plant species from coastal sand dunes, Anthyllis maritima. The particular hypothesis tested was that there is an interaction between sand burial, rhizobial symbiosis and salt treatment at the level of physiological responses. Experiment in controlled conditions included 18 treatment combinations of experimental factors, with two intensities of sand burial, rhizobial inoculation and two types of NaCl treatment (soil irrigation and foliar spray). Shoot biomass was significantly affected both by burial and by inoculation, and by interaction between burial and NaCl in the case of shoot dry mass. For plants sprayed with NaCl, burial had a strong significant positive effect on shoot growth irrespective of inoculation. General effect of inoculation with rhizobia on shoot growth of plants without NaCl treatment was negative except for the plants buried 2 cm with sand, where significant stimulation of shoot dry mass by inoculant was found. The positive effect of burial on shoot growth was mainly associated with an increase in leaf petiole height and number of leaves. Performance index significantly increased in buried plants in all treatment combinations, and leaf chlorophyll concentration increased in buried plants independently on burial depth, and only in plants not treated with NaCl. Inoculation led to significant increase of leaf peroxidase activity in all treatment combinations except NaCl-irrigated plants buried for 2 cm by sand. Sand burial stimulated peroxidase activity, mostly in non-inoculated plants, as inoculation itself led to increased enzyme activity. In conclusion, strong interaction between sand burial and NaCl treatment was evident, as the latter significantly affected the effect of burial on growth and physiological indices. Moreover, rhizobial symbiosis had a significant effect on physiological processes through interaction with both sand burial and NaCl treatment, but the effect was rather controversial; it was positive for photosynthesis-related parameters but negative for growth and tissue integrity indices.

Impact of Electron Beam Irradiation on the Bioactive Principles of Seeds of Coastal Sand Dune Wild Legumes (Canavalia spp.).

BACKGROUND: Recent patents reveal that vegetable ingredients have several applications in novel food formulations. Many so-called antinutritional components (e.g. tannins, saponins, lectins and protease inhibitors) have nutraceutical as well as pharmaceutical significance. Seeds of two wild legumes of the genus Canavalia inhabitants of the coastal sand dunes of Southwest India are known for a variety of bioactive principles (e.g. phenolics, tannins, canavanine, concanavalin and phytohemagglutinins). OBJECTIVE: This study evaluates the impact of Electron Beam (EB) irradiation on the bioactive components of seeds of two coastal sand dune wild legumes Canavalia cathartica and C. maritima. METHODS: The dry seeds of C. cathartica and C. maritima were EB irradiated with different doses (2.5, 5, 10 and 15 kGy) to follow changes in six bioactive principles (total phenolics, orthodihydric phenols, tannins, canavanine, trypsin inhibitors and phytohemagglutinins) in comparison to control seeds. One-way ANOVA was employed to follow the variation in bioactive components of seeds in control and different doses of irradiation. RESULTS: Seeds of both legumes were devoid of orthodihydric phenols and trypsin inhibitors. In C. cathartica, the total phenolics showed significant dose-dependent increase up to 5 kGy and decreased thereafter. Tannin content was not altered up to 10 kGy followed by significant decrease at 15 kGy. There was no significant change in canavanine content and the phytohemagglutinin activity against human erythrocytes was not altered. Seeds of C. maritima did not show significant changes in total phenolics as well as tannin contents. The content of canavanine showed significant dose-dependent increase up to 5 kGy followed by significant decrease. There was no variation in phytohemagglutinin activity against erythrocytes A, B and O, while against AB, the activity decreased at 2.5 kGy and further decrease was constant at higher doses. CONCLUSION: The EB irradiation doses employed have selectively altered the bioactive principles of Canavalia seeds and such treatments may facilitate to maneuver desired medicinal, nutritional, functional and cooking properties. Besides selective changes in bioactive components the seeds have extended shelf life.

Widespread Distribution of Highly Adapted Bradyrhizobium Species Nodulating Diverse Legumes in Africa.

Bradyrhizobium is one of the most cosmopolitan and diverse bacterial group nodulating a variety of host legumes in Africa, however, the diversity and distribution of bradyrhizobial symbionts nodulating indigenous African legumes are not well understood, though needed for increased food legume production. In this review, we have shown that many African food legumes are nodulated by bradyrhizobia, with greater diversity in Southern Africa compared to other parts of Africa. From a few studies done in Africa, the known bradyrhizobia (i.e., Bradyrhizobium elkanii, B. yuanmingense) along with many novel Bradyrhizobium species are the most dominant in African soils. This could be attributed to the unique edapho-climatic conditions of the contrasting environments in the continent. More studies are needed to identify the many novel bradyrhizobia resident in African soils in order to better understand the biogeography of bradyrhizobia and their potential for inoculant production.

Bacteria from nodules of wild legume species: Phylogenetic diversity, plant growth promotion abilities and osmotolerance.

The demand for food with high nutritional value that can sustain the growth of human population while safeguarding sustainability deserves urgent attention. A possible strategy is the inoculation of crops with plant growth promoting (PGP) bacteria. Plants are naturally colonized by bacteria that can exert beneficial effects on growth and stress tolerance. N2 fixation by rhizobia in the root nodules of legumes is a well-known PGP effect. These bacteria can be used as inoculants to boost legumes productivity and can be especially interesting if they are able to survive to abiotic stresses, such as drought. Herein we report the phylogenetic diversity of bacteria colonizing the root nodules of several wild legume species, from four geographic locations in Portugal with different bioclimates. Interestingly, the vast majority of strains belonged to Flavobacterium, Pseudomonas and other genera apart from rhizobia. PGP abilities other than N2 fixation (production of indol acetic acid, siderophores and volatile organic compounds) and osmotolerance were screened. Location and host plant species did not influence PGP abilities and osmotolerance. Taken together, results evidenced that bacterial strains from wild legumes displaying PGP abilities and osmotolerance can be regarded as good candidates for inoculants of a broad range of hosts, including non-legumes.

Impact of Electron-Beam Irradiation on Functional Attributes of Seeds of Two Coastal Wild Legume Landraces of Canavalia.

BACKGROUND: Vegetable proteins have widespread application in the food industry as functional ingredients in food formulations according to the recent patents. Requirement to develop less expensive protein-rich supplementary foods has resulted in shift of emphasis towards lesser known wild than popular legumes. OBJECTIVE: The aim of this study is to expose seeds of two coastal sand dune wild legumes of the Southwest India (Canavalia cathartica and C. maritima) to different doses of electron-beam (EB) irradiation to assess changes in functional attributes. METHOD: Intact dried seeds were exposed to EB irradiation (2.5, 5, 10, 15 kGy). Protein solubility, gelation concentration, water-absorption capacity, oil-absorption capacity, emulsion properties and foam properties of control and irradiated seeds were assessed by standard methods. RESULTS: Protein solubility of both seed flours attained the highest at 2.5 kGy, followed by gradual dosedependent decrease. The gelation concentration increased in C. cathartica only at 5 kGy, while it decreased in C. maritima at 2.5 kGy without further change at higher doses. The water-absorption capacity of C. maritima was significantly higher than C. cathartica in control sample, while at 15 kGy C. cathartica showed significantly higher absorption capacity than C. maritima. The oil-absorption capacity was significantly higher in C. maritima than C. cathartica in control as well as all doses of irradiation. Emulsion activity of C. maritima was slightly higher than C. cathartica in control and irradiated samples, while both seeds showed similar emulsion stability in control with significant increase in C. cathartica at 10 kGy and 15 kGy. The foam capacity in both seeds was similar up to 2.5 kGy followed by significant increase in C. maritima at 5 kGy and 10 kGy. The foam stability was significantly higher C. cathartica than C. maritima in control as well as in irradiated samples. The foam capacity was higher in C. maritima than C. cathartica in control and irradiated samples, which showed gradual time-dependent decrease in stability with higher stability at 8 hr in C. cathartica than C. maritima. CONCLUSION: Improved functional properties (protein solubility, emulsion stability and foam capacity) and decreased gelation concentration in seeds of C. maritima irradiated at 5 kGy is advantageous in the production of functional foods. Even though both species of Canavalia grew on the coastal sand dunes and their seeds were exposed to same doses of radiation, they differed in functional attributes confirm that it is species-specific. Canavalia seeds being rich in proteins, carbohydrates, essential amino acids, essential fatty acids and bioactive components, further studies on the impact of EB irradiation helps in optimization of nutraceutical potential as well as functional attributes for future applications.