Characterization of root nodule and rhizobium of a leguminosae ephemeral plant- Trigonella arcuata C.A.Mey in Xinjiang

Abstract:

[Objective] We studied root nodule proliferation, nodule microstructure, genetic cluster and stress resistance of the rhizobium of Trigonella arcuata. [Methods] We characterized root nodule and rhizobium with various soil matrixes cultivation, paraffin section, resin semi-ultrathin section techniques, and 16S rRNA gene cluster analysis. [Results] ① Plants grew in mixed soil (nutritious garden soil∶poplar zone soil∶desert sands=1∶1∶1), had the most nodule prolif-eration and bore the most pods. The shapes of nodule were palm- or ginger-like; ② Microstructure of the nodule revealed five different parts differentiated within the nodule: epidermis(E), cortex(C), vascular bundle(VB), infected cells(IC) and uninfected cells(UIC); ③ Genetic cluster analysis of the full length 16S rRNA gene sequence (1377 bp) indicated that the rhizobium isolated shared the highest identities with Sinorhizobium meliloti; ④ The rhizobium could grow between 4 and 60℃ (20 min), pH 6.0~12.0 and 0~2%NaCl. For the antibiotic sensitivity, the rhizobium could not grow normally in me-dium with 25 mg/mL Kanamycin, Streptomycin or Cephalothin, except for 100 mg/mL Ampicillin. [Conclusion] Good conditions of soil matrixes were important for nodulation of T. arcuata; A large quantity of cells in fascicular nodules were infected by rhizobia; 16S rRNA gene sequence of T. arcuata shared the highest identities with that of Sinorhizobium meliloti, and this strain was able to tolerate relatively higher temperature and alkalin.