Symbiotic effectiveness of potential Bradyrhizobium/Ensifer strains ongrowth, symbiotic nitrogen fixation and yield in soybean [Glycine Max (L.)]

Symbiotic nitrogen fixation (SNF) is a mutualistic interaction between host plant and the root nodule bacteria. The present investigation was carried out to study symbiotic effectiveness of potential Bradyrhizobium (slow growing; IND1, LSBR3, PANT1, SB271, & DS1) / Ensifer (fast growing; IND2, LSER7, LSER8 & PANT2) strains over uninoculated control on growth and yield in soybean [Glycine max (L.)]. In-vitro thin layer chromatographic (TLC) analysis revealed significantly high amount of flavonoid like compounds from roots of soybean seeds bacterized with LSBR3 (3.44 μg/ml) as compared to control treatment (2.60 μg/ml). Field evaluation of potential rhizobia presented significantly higher germination and plant height with Ensifer strains, LSER8 (94.7% and 36.8 cm), LSER 7 (93.4% and 36.4 cm) and Bradyrhizobium strain LSBR3 (91.5% and 35.6 cm), respectively. Overall microbial activity assayed by dehydrogenase activity was significantly higher for LSBR3 (17.54 μg/TPF/g/soil/h) and LSER7 (16.75 μg/TPF/g/soil/h) at 90 DAS as compared to other treatments. Nodulation significantly enhanced with LSER8 and LSER7 (ranged from 52.2 to 135.7 and 49.9 to 128.7 mg/plant, respectively) treatments over un-inoculated control. Maximum leghaemoglobin and nitrogen content (5.52 mg/g fresh weight of nodules and 2.89 %, respectively) analyzed with LSBR3. Grain yield recorded was significantly higher with LSBR3 (12.3%) followed by PANT1 (12 %) and LSER8 (11.7%) over control and emerged as effective strains for improving growth, SNF and yield in soybean and can be exploited as commercial inoculants of soybean