Symbiotic effectiveness of Rhizobium (Agrobacterium) compared to Ensifer (Sinorhizobium) and Bradyrhizobium genera for soybean inoculation under field conditions

Abstract

The symbiotic potential of twenty Egyptian strains of soybean-nodulating rhizobia related to Agrobcaterium (Rhizobium), Ensifer (Sinorhizobium) and Bradyrhizobium genera has been evaluated under greenhouse and sandy loam-field soil conditions. Greenhouse-screening results showed positive symbiotic interactions between all tested rhizobia and soybean cultivar, Giza 22. The growth parameters and N-shoot content of the inoculated soybean plants were clearly affected and appeared depending upon rhizobial strain type. Four promising rhizobial strains (Ensifer NGB-SR3, Bradyrhizobium NGB-SR4, Agrobcaterium NGB-SR7, Bradyrhizobium NGB-SR14) were tested for soybean inoculation under field conditions. During flowering stage, there was a prolific nodulation pattern with all tested inoculants resulted in nodule masses ranged from 265-361 mg plant-1, compared to the un-inoculated control (15-31 mg plant-1). At harvest, the superiority of Bradyrhizobium NGB-SR4 and Agrobcaterium NGB-SR7 over other tested rhizobia was evident regarding soybean seed yield, seed N-yield and crude protein content. We confirm the nodulating machinery stability of Agrobacterium under greenhouse and sandy loam field soil conditions and their potential use as efficient soybean inoculants along with other traditional soybean micro-symbionts; Bradyrhizobium and Sinorhizobium genera. © 2014 Academic Journals Inc.