Abstract
This study was conducted to 1) isolate and characterize some rhizobia from some legumes, 2) determine the phylogenetic relationships among them; and 3) investigate their potential biological control agent. 24 Rhizobial isolates were obtained from five legumes namely; faba bean, lentil, pea, clover, and soybean. Morphological characterization classified isolates into fast grower and slow grower. Also, their biochemical profiles using API 20E and API 20NE system showed large diversity which may reflect their adaptation in different environments. Moreover, molecular detection by 16S rDNA gene was able to characterize 19 of them to species level. Isolates from pea, faba bean, clover and lentil were Rhizobium leguminosarum and isolates from soybean were Bradyrhizobium japonicum. This data supported the idea that there is a narrow diversity of species of rhizobia in Egypt. Phylogenetic analysis of the 19 isolates confirmed that the Bradyrhizobium japonicum isolates were phylogenetically divergent from all other isolates. Also, the phylogram revealed that each group of isolates originated from root nodule of a certain legume formed a separate sub-cluster. Besides a narrow range of interspecies variations was found which is consistent with the idea of biovars presence among species. In addition, the 24 isolates showed strong inhibition of growth of Fusarium and Rhizoctonia phytopathogens. However, results indicated that 25% of isolates were not able to solubilize tricalcium phosphate. On the other hand, the IAA production by the 24 isolates varied greatly among isolates. Therefore, these results demonstrated that they may have the potential to act as biocontrol agents. Moreover, we characterize Nod D gene on the molecular level. Upon its isolation its size came to be 820 bp of nucleotides. This came to be true for all bacterial isolates except four isolates we did not succeed to isolate NodD gene. Moreover we used Quantitative Real Time PCR to study NodD gene expression. Seven nod D gene were down regulated and five were up regulated than 16S housekeeping gene.
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