Genetic diversity and distribution of rhizobia associated with the medicinal legumes Astragalus spp. and Hedysarum polybotrys in agricultural soils.
With the increasing cultivation of medicinal legumes in agricultural fields, the rhizobia associated with these plants are facing new stresses, mainly from fertilization and irrigation. In this study, investigations on the nodulation of three cultivated medicinal legumes, Astragalus mongholicus, Astragalus membranaceus and Hedysarum polybotrys were performed. Bacterial isolates from root nodules of these legumes were subjected to genetic diversity and multilocus sequence analyses. In addition, the distribution of nodule bacteria related to soil factors and host plants was studied. A total 367 bacterial isolates were obtained and 13 genospecies were identified. The predominant microsymbionts were identified as Mesorhizobium septentrionale, Mesorhizobium temperatum, Mesorhizobium tianshanense, Mesorhizobium ciceri and Mesorhizobium muleiense. M. septentrionale was found in most root nodules especially from legumes grown in the barren soils (with low available nitrogen and low organic carbon contents), while M. temperatum was predominant in nodules where the plants were grown in the nitrogen-rich fields. A. mongholicus tended to be associated with M. septentrionale, M. temperatum and M. ciceri in different soils, while A. membranaceus and H. polybotrys tended to be associated with M. tianshanense and M. septentrionale, respectively. This study showed that soil fertility may be the main determinant for the distribution of rhizobia associated with these cultured legume plants.
['Yan|Hui|H|', 'Ji|Zhao Jun|ZJ|', 'Jiao|Yin Shan|YS|', 'Wang|En Tao|ET|', 'Chen|Wen Feng|WF|', 'Guo|Bao Lin|BL|', 'Chen|Wen Xin|WX|']
D021903:DNA, Ribosomal Spacer D007887:Fabaceae D014644:Genetic Variation D058885:Multilocus Sequence Typing D010802:Phylogeny D012336:RNA, Ribosomal, 16S D012231:Rhizobium D053204:Root Nodules, Plant D012988:Soil Microbiology D013559:Symbiosis
Genetic diversity Distribution Rhizobia Astragalus Mesorhizobium