الفهرس 
Soil and plant samplingOnly 14 pages are availabe for public view
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Abstract
Generally, leguminous plants play a very important ecological and agricultural active role in the process of biological nitrogen fixation. These plants characterized by their ability to establish N2-fixing symbiotic associations with Alphaproteobacteria of the genra Azorhizobium, Bradyrhizobium, Mesorhizobium, Rhizobium, and Ensifer collectively referred as rhizobia. The legume–Rhizobium symbiosis constitute a significant source of N, consequently play an essential role in soil fertility. The global N from the symbiotic nitrogen fixers (SNF) in the agricultural system is 50–70 Tg annually.
Growing interest with the unexplored biogeographical regions provide evidence of enormous diversity among the nitrogen-fixers and nodulating bacteria of the wild grown legumes.
The bacterial symbiosis genes which are essential for the establishment of an effective symbiosis, can be divided into two categories; nodulation genes, which are responsible for nodulation, and nitrogen fixation genes that are involved in atmospheric nitrogen fixation. Although nod genes are specific to rhizobia, nif genes were found in many bacteria.
Mellilotus indicus, sometimes incorrectly written Melilotus indica, is a yellow-flowered herb native to northern Africa, Europe and Asia. It`s used as forage and as a soil improver.
The present study aimed to study the natural bio-diversity and the genetic convergence of the rhizobial strains isolated from root nodules of Mellilotus indicus, from different habitats, by conducting and analyzing some morphological, physiological and genetical experiments.
The plants of Melilotus indicus were collected from different habitats in Egypt. Then, the rhizobial bacteria were isolated and purified from the roots of Melilotus indicus plants. The morphological properties of the isolates were
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studied. Some of the physiological properties such as the effect of salinity, high and low temperature, pH have been studied. Also, the ability of the different rhizobial isolates to use different carbon sources, to resist some antibiotics, the heavy metals effect on the growth of these isolates were studied. Furthermore, their ability to solublize phosphorus and to produce acetic acid and hydrogen cyanide, as well as their antagonistic activity against some soil born fungi were tested. All the obtained results were analyzed statistically to determine the degree of relatedness of the isolates to each others.
Soil samples were collected from the different habitats of collected plants. Their physical and chemical properties were determined.
Finally, the genetic polymorphism between the rhizobial isolates were determined by screening the DNA of the different rhizobial isolates using different genetic tools like nodC, rep-PCR and RAPD-PCR to clarify natural variation that might be present between the rhizobial isolates.