Potential of Rhizobium spp. for improving growth and yield of rice (Oryza sativa L.)

The ability of Rhizobium to colonize roots of certain cereals and promote their growth and yield at harvest has been proven experimentally involving a number of mechanisms which were independent of root nodulation and biological N-2-fixation. Various rhizobial strains i.e. Rhizobium phaseoli (A2, A3, S17, N8), Rhizobium leguminosarum (LSI-23, LSI-26, LSI-29, LSI-30) and Mesorhizobium ciceri (CRI-28, CRI-31, CRI-32, CRI-38) isolated from the nodules of mung bean, lentil and chickpea, respectively, were tested for their potential to promote growth and yield of rice grown in potted soil. Seedlings of rice cultivar "Super Basmati" were transplanted in pots after inoculation with test strains of rhizobium. The fertilizers, P and K were applied at 60-60 kg ha(-1) as a basal dose while N was applied at 120 kg ha(-1) in two splits. Good quality canal water was used for irrigation. Most of the parameters i.e. number of tiller(1) (46%); paddy yield (43%), plant biomass (18%), straw dry weight (45%) and 1000-grain (25%) improved maximally by the strain LSI-29 over un-inoculated control. Whereas, in case of plant height, and number of grains panicle(-1), strain A2 caused maximum increase up to 28 and 29%, respectively over un-inoculated control. Furthermore, both the strains i.e. LSI-29 and A2 gave significant increase in nitrogen, phosphorus and potassium contents of paddy. It is concluded that all the tested rhizobial strains have the potential to enhance the growth and yield of rice, however, LSI-29 and A2 may have better prospects. Moreover, further work is needed to explore the effectiveness of these strains under field conditions.