الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 213 |  |  |
| | | from | 213 | | |
Abstract
The Present study aims to the isolation and characterization of Rhizobium and Bradyrhizobium strains from root nodules of some leguminous plants in Minia governorate according to biochemical and molecular tools. Pink nodules were selected from 45-90 days legume plants to isolate rhizobia. Rhizobium was recovered from Vicia faba, Pisum sp., Lens sp., Trigonella sp. and Trifolium sp., while Glycine max & Arachis hypogea were the host plants for Bradyrhizobium in this study. On YEMA-CR medium, the colonies were circular, very pale white (watery) to white, mucoid, opaque to transparent and with high convex entire margin. Only one isolate of peanut (1BPe) were pale pink. Rhizobium isolates were fast growing giving colonies with 2-5 mm in diameter after 5 days. Those of Bradyrhizobium were slow growing as the diameter didn’t reach 1mm after 7 days (i.e: point) and all were gummy (jelly-like) except 1BPe that was sticky and had little mucus. According to morphological features, isolates were divided into different groups. Both genera are Gram-negtive, thin rods and motile. The efficiency of isolated strains to fix N2 was then tested in pots containing soil; this soil autoclaved twice to ensure sterility. The cultivation process was carried out during the 2011-2012 (for winter plants) and summer of 2013 for soybean and peanut, using pots of 15 cm diameter X 20 cm deep pots containing 1200 g of autoclaved soil. Each isolate was inoculated into the corresponding plants. At 60 days after sowing, all plants were harvested. Lengths and dry weights were measured. The percentage of N2 was estimated using Kjeldahl method. Analysis of variance (ANOVA) was also performed on data of all plant parameters measured using the SAS software package. Also, the strains of high efficiency were selected for sequencing using 16S rRNA gene. Members of the same group often gave the same results of biochemical tests. All Rhizobium isolates were acid producers when grown on YEMA-BTB, but Bradyrhizobium gave blue color indicating alkali production. from the present study we could obtain some isolates with promising characters: The ability to grow over a wider range of pH and resisted alkalinity (pH 11.2), salinity (up to 3% NaCl), temperature (40 ºC), antibiotic resistance ability and carbon sources utilization (e.g: 14RV, 1RH and 2RHb).These characteristic may be responsible for their saprophytic persistence in the soil and withstanding adverse conditions like high salinity, heat and alkalinity. Our results indicate that the inoculation of Rhizobium and Bradyrhizobium isolates to plant significantly increased nodule numbers, the plant growth and nitrogen content of Vicia faba, Pisum sp., Lens sp., Trigonella sp. and Trifolium sp., Glycine max & Arachis hypogea. All the isolates of Bradyrhizobium can secrete amylase that has great significance in present-day biotechnology, having approximately 25% of the enzyme market.