Rhizospheric rhizobia with potential as biofertilizers from Cuban rice cultivars

Rice biofertilization with Rhizobium increases the growth and yield of the crop. However, evidence for this has not been observed in Cuban rice cultivars. This research aimed to typify two Rhizobium isolates, considering the use of different carbon sources, their tolerance to stress conditions, and the ability to promote the growth and development of rice. Two Rhizobium sp. isolates (Rpr11 and 5P1) were used and their facility to grow on different carbon sources, pH, and salinity levels was determined. The effect of the inoculation of these bacteria on the growth and yield of rice was evaluated under controlled, greenhouse, and field conditions. Both isolates grew on mannitol, glycerol, maltose, and fructose at the highest concentrations of NaCl (1.0, 1.5 and 2.0%). The isolate 5P1 grew at all evaluated pH levels, especially at pH 5.0 and pH 8.0. The inoculation of both isolates increased the plant biomass and the potassium content. The plants inoculated with 5P1 had the highest contents of nitrogen, total chlorophyll, carbohydrates and proteins, and grain yield. This study is the first in Cuba that shows the beneficial effect of Rhizobium inoculation on the physiology and yield of rice.