Development of root nodule rhizobial strains with better tolerance to environmental stresses using molecular genetics techniques


Introduction

Leguminous plants can obtain most of nitrogen they need from the vast supply of gaseous nitrogen in the air. They gather and use this nitrogen by working symbiotically with special bacteria (rhizobia) in nodules on their roots. Rhizobia infect the root hairs of the leguminous host; nodules develop and become small nitrogen factories on the legume roots.
Rhizobia are commonly found in soil, but often they fail to produce effective nodulation due to the effects of genetic and ecologic parameters.
Different ecological factors are dramatically affecting the legume/rhizobia symbiosis, (e.g., salinity, heat, heavy metals and drought), which can preclude legume establishment and growth or reduce crop yield.
Molecular genetics is a useful tool for development of efficient N2-fixation Rhizobium; where the incensement of plant production through Biological Nitrogen Fixation (BNF) of these microorganisms must be enhanced.

Objectives


This proposal aims to isolate, identify and characterize different indigenous Rhizobium strains from different geographical areas. These strains are usually more adapted than the added inoculants for environmental selection. They will be selected according to some characters relates to competition ability within the same species (bacteriocins) or due to some other ecological factors, e.g., salt, drought or heavy metals, to select the best strains for each ecological area. The selected strains will be characterized genetically, i.e. plasmid profile and DNA finger printing.
This project also aims to improve nodulation efficiency, salt-tolerant, drought tolerant, heavy metal resistant, bacteriocin production and / or immunity and expanded host range among some selected strains by using molecular genetics techniques.