Horizontal Gene Transfer and Recombination Shape Mesorhizobial Populations in the Gene Center of the Host Plants Astragalus Luteolus and Astragalus Ernestii in Sichuan, China

Mesorhizobium sangaii sp. nov., isolated from the root nodules of Astragalus luteolus and Astragalus ernestii

“…Astragalus luteolus and Astragalus ernestii are wild plants that grow at altitudes above 3000 m. Astragalus ernestii grows only in western Sichuan, north-west of Yunnan and in eastern Tibet. Astragalus luteolus is an indigenous endemic plant species grown in western Sichuan province (Li et al, 2009b).…”

“…In our previous study, 33 rhizobial strains were isolated from the root nodules of Astragalus luteolus and Astragalus ernestii growing on the west plateau at two different altitudes in Sichuan province, China. A total of 28 strains were classified as members of the genus Mesorhizobium by using amplified 16S rRNA gene restriction analysis, amplified fragment length polymorphism, BOX element-PCR fingerprinting, 16S rRNA gene sequence analysis and other molecular characterization methods (Li et al, 2009b). The results revealed that the two strains SCAU7 T and SCAU27 exhibited distinct characteristics and differed from the known species of the genus Mesorhizobium.…”

“…Seeds were incubated to allow germination in sterile Petri dishes at 25 u C (Vidal et al, 2009). Plants were transferred into pots filled with vermiculite moistened with an N-free plant nutrient solution (Vincent, 1970).The pots were maintained in a growth chamber at 28 u C with a photoperiod of 15 hours light: 9 hours dark (Li et al, 2009b). After 7 weeks, plants were harvested and analysed for nodule occurrence.…”