Bradyrhizobium yuanmingense related strains form nitrogen-fixing symbiosis with Cajanus cajan L. in Dominican Republic and are efficient biofertilizers to replace N fertilization

Abstract

Cajanus cajan L. is a legume whose green seeds are consumed in Caribean countries such as Dominican Republic where is a horticultural plant highly appreciated by the consumers. In this work we isolated several slow-growing rhizobial strains nodulating C. cajan that were found to be closely related to Bradyrhizobium yuanmingense according to the analysis of 16S rRNA gene sequences. These strains were genetically diverse on the basis of their RAPD patterns and showed high variability in nodulation ability and N-fixation on hydroponic conditions. Highly effective strains used as biofertilizers in four different soils from Dominican Republic showed that biofertilization of C. cajan with these strains produced the same or even higher yield than the mineral nitrogen fertilization. Therefore, biofertilization with native Bradyrhizobium strains can be adopted instead of chemical fertilization to improve both the yield and the quality of C. cajan. This is the first report about the nodulation of this legume by strains close to B. yuanmingense in Dominican Republic where the natural nodulation of C. cajan is scarce and then, the biofertilization can be crucial to increase the yield of this horticultural crop very important for human feeding.