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Host range nodulation and adaptation in frenchbean rhizobia
B Dhar1, Ashok Mishra, M K Singh
1Laboratory of Biological Nitrogen Fixation, Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, B.H.U., Varanasi 221 005, India.
Indian Journal of Experimental Biology
|March 17, 2006
Summary
Frenchbean rhizobia strains showed improved nodulation and nitrogen fixation on new legume hosts. Passage through alternate hosts enhanced their symbiotic efficiency without altering genetic markers.
Area of Science:
- Agricultural Science
- Microbiology
- Plant Science
Background:
- Rhizobial strains are crucial for legume nitrogen fixation.
- Understanding rhizobial host range and efficiency is vital for sustainable agriculture.
- Frenchbean rhizobia's adaptability to diverse legume hosts requires further investigation.
Purpose of the Study:
- To evaluate the host range and nodulation efficiency of genetically marked frenchbean rhizobial strains.
- To assess the impact of passage through different legume hosts on rhizobial symbiotic performance.
- To investigate potential modifications in rhizobial symbiotic behavior and genetic stability.
Main Methods:
- Testing four genetically marked frenchbean rhizobial strains (HURR-3, Raj-2, Raj-5, Raj-6) on five legume hosts: frenchbean, pigeonpea, mungbean, urdbean, and soybean.
- Re-isolating rhizobia from nodules formed on both main and alternate hosts.
- Assessing nodulation efficiency and nitrogen fixation improvements in re-isolated strains.
- Analyzing phage-susceptibility and intrinsic antibiotic resistance to monitor genetic stability.
Main Results:
- Frenchbean rhizobia nodulated frenchbean, mungbean, and urdbean, but not soybean or pigeonpea, initially.
- Strains HURR-3 and Raj-5, after isolation from nodules on alternate hosts (mungbean, urdbean), showed enhanced nodulation and nitrogen fixation efficiency.
- These adapted strains demonstrated an expanded host range, successfully nodulating pigeonpea in addition to mungbean and urdbean.
- Genetic markers (phage susceptibility and antibiotic resistance) remained unchanged after passage through different hosts.
Conclusions:
- Frenchbean rhizobia can adapt to a wider host range, including pigeonpea, mungbean, and urdbean, through passage on alternate hosts.
- This adaptation enhances symbiotic efficiency without altering the genetic markers of the rhizobial strains.
- The findings suggest modifications in symbiotic behavior, enabling frenchbean rhizobia to adapt to diverse legume hosts.
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