Diversity of Rhizobium-Phaseolus vulgaris symbiosis: overview and perspectives
ABSTRACT Common bean (Phaseolus vulgaris) has become a cosmopolitan crop, but was originally domesticated in the Americas and has been grown in Latin America for several thousand years. Consequently an enormous diversity of bean nodulating bacteria have developed and in the centers of origin the predominant species in bean nodules is R. etli. In some areas of Latin America, inoculation, which normally promotes nodulation and nitrogen fixation is hampered by the prevalence of native strains. Many other species in addition to R. etli have been found in bean nodules in regions where bean has been introduced. Some of these species such as R. leguminosarum bv. phaseoli, R. gallicum bv. phaseoli and R. giardinii bv. phaseoli might have arisen by acquiring the phaseoli plasmid from R. etli. Others, like R. tropici, are well adapted to acid soils and high temperatures and are good inoculants for bean under these conditions. The large number of rhizobia species capable of nodulating bean supports that bean is a promiscuous host and a diversity of bean-rhizobia interactions exists. Large ranges of dinitrogen fixing capabilities have been documented among bean cultivars and commercial beans have the lowest values among legume crops. Knowledge on bean symbiosis is still incipient but could help to improve bean biological nitrogen fixation.
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ABSTRACT: The development of legume nodules and N2-fixation demand fair proportion of photosynthetic carbon (C). Soil as a determinant of nodulation may influence C allocation to nodule and subsequent underground C fates. However, there is little information on the photosynthetic C allocation to the nodule of soybean grown in Mollisols in Northeast China. Such research is crucial for optimizing the strategies of C/N management to improve nodulation and productivity in soybean farming systems. With a pot experiment, soybean plants were grown in three Mollisols sampled from low- to high-latitude in Northeast China and labeled with 13CO2 at the R4 (full pod) and R5 (initial pod filling) stages. The nodule characteristics and underground 13C distribution were investigated. The nodule number and nodule density were in the order of Mid- > High- > Low-latitude Mollisol, resulting in 980, 578 and 252 nodules per plant, and 11.1, 8.2 and 2.7 nodules per m of root length, respectively. The 13CO2 pulse-chase labeling showed that higher proportion of 13C was recovered in Mid-latitude Mollisol at R4, and in both Mid- and High-latitude at R5. Moreover, a 53.8% of increase on C-growth rate of nodule was also found in the two soils compared to Low-latitude. This suggests that nodules in high-latitude Mollisols have stronger C-sink activity than low-latitude ones, which attribute to nodule number and C-growth rate of nodule. The nodules accounted for 15.7%, 28.0% and 11.5% of net underground 13C in Low-, Mid- and High-latitude Mollisols, respectively. Therefore, the extent of nodule-driving underground C allocation varied with Mollisols from geographically different regions.European Journal of Soil Biology 05/2014; · 1.84 Impact Factor
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ABSTRACT: We have analyzed 30 rhizobial isolates obtained from common bean (Phaseolus vulgaris L.) root nodules grown in the Middle Blacksea Region of Turkey, using ARDRA and nucleotide sequence data. ARDRA analysis with enzymes CfoI, HinfI, NdeII, MspI and PstI revealed three patterns. Based on sequence data from 16S rDNA, the patterns were identified as, Rhizobium leguminosarum bv. phaseoli (n = 16), R. etli bv. phaseoli (n = 8) and R. phaseoli (n = 6). On the other hand, nucleotide sequence phylogenies of housekeeping genes (recA, atpD and glnII) selected to confirm the 16S rDNA phylogeny revealed different evolutionary relationships. These results suggested the possibility of lateral transfers of these genes amongst different rhizobial species (including R. leguminosarum, R. etli and R. phaseoli) sharing the same ecological niche (nodulating P. vulgaris) which also indicates that there may be no true genetic barier among these species. Phylogenetic analysis based on DNA sequence data from the nodA and nifH genes showed that all rhizobial species obtained in this study were carrying nodA and nifH haplotypes which were the same or similar to those of CFN42 (R. etli type strain), suggesting a further support for the lateral transfer of CFN42 Sym plasmid, p42, amongst Turkish common bean nodulating rhizobial isolates.Annals of Microbiology · 1.55 Impact Factor
- Agricultural and Food Science 01/2014; 23(3):173-185. · 0.79 Impact Factor