Genetic characterization of heavy metals tolerant mutants of rhizobia nodulating Pisum sativum

This work was conducted in the genetics laboratory -Faculty of Agriculture, Menoufia University. It was carried out to investigate the interaction between Rhizobium strains isolated from contaminated agricultural soils with heavy metals and Pisum sativum (Pea) plants. The study's goals were: 1- Isolation and identification of Rhizobium isolates from different polluted sites cultivated with Pisum sativum. 2- In vitro evaluation of isolates' tolerance to three heavy metals (Cobalt, Nickel, and Lead) 3- Assessment of the impact of the most tolerant isolates on pea plants under greenhouse conditions. 4- Induction of Rhizobium mutants more tolerant to lead (Pb) by EMS and assessment of their effect on pea plant parameters. To achieve our goals, twenty-three agricultural sites representing different Governorates (Menoufia, Gharbia, Kafr El Sheikh, Qalubia, Giza, Ismailia, Daqahlia, Sharqia, and Behira) irrigated with wastewater were selected for sampling. A total of 25 Rhizobium isolates were collected from pea root nodules and characterized morphologically, biochemically, and molecularly through 16S rDNA sequencing, confirming their identity as Rhizobium leguminosarum. The data obtained were summarized as follows: