Rhizobium, a root nodule bacterium, has the ability to fix atmospheric nitrogen in symbiotic association with host legumes. It was estimated that a total of 175 million metric tones of N is fixed per year globally through biological nitrogen

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INTRODUCTION
Rhizobium, a root nodule bacterium,
has the ability to fix atmospheric nitrogen in
symbiotic association with host legumes. It was
estimated that a total of 175 million metric
tones of N is fixed per year globally through
biological nitrogen fixation involving Legume
Rhizobium symbiosis. Rhizobia invade the roots of
legume plants through root hairs, form effective
pink colored nodules in the tap or lateral roots
and lives symbiotically inside the nodules to fix
nitrogen to plant accessible forms.
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Rhizobium as component of INM
Rhizobium, a root nodule bacterium, has the
ability to fix atmospheric nitrogen in
symbiotic association with host legumes.It
was estimated that a total of 175 million
metric tones of N is fixed per year globally
through biological nitrogen fixation
involving Legume Rhizobium symbiosis
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HOW RHIZOBIA INFECT LEGUME ??
Curling of root hair Invagination
point Infection thread develop Bacteria released
Nodular tissue develop
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ISOLATION AND MAINTENANCE OF RHIZOBIUM
Selection of legume crops
Collection of nodules
Rhizobium isolation in media
Preservation in slant
Nodulation tests
Purified rhizobial cells
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CHARACTERISTICS OF RHIZOBIUM
Rhizobia invade legume roots through
root hairs Form effective pink colored nodules
in the roots Lives symbiotically inside the
nodules and fix nitrogen Converts atmospheric
nitrogen to plant accessible forms Most
rhizobia are host specific in nature
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RHIZOBIUM CONTRIBUTES
50 200 KG NITROGEN PER HECTARE PER CROP
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Rhizobium Inoculation and Crop Response
Inoculation Method
Rhizobium culture
Nitrogen Fixation
Crop Response
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Contribution of Rhizobium in biological N
fixation
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LET US SUM UP
Rhizobium fix atmospheric nitrogen in symbiotic
association with host legumes. It was
estimated that a total of 175 million metric
tonnes of N is fixed per year through
legume-Rhizobium symbiosis. Rhizobium lives
symbiotically inside the nodules and fix nitrogen
which is converted to plant accessible forms.

Contd..
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Contd..
Rhizobia invade the roots of legume plants
through root hairs and form effective pink
colored nodules in the tap or lateral roots.
Most Rhizobia are host specific and nodulate
specific legumes.
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ASSESSMENT
Q. Choose the correct answer i) From which
crop do you expect to isolate Rhizobium? a)
Cereal crops c) Legumes
b)Oilseeds d)
Grasses ii) How much Nitrogen does Rhizobium
contribute? a)10-50 kg
c) 200-250 kg b)50-200 kg
d) 400-500 kg

Contd
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Contd iii) How much rhizobial culture required
inoculate 30 M ha legume crop? a) 5,000
tonnes c) 15,000 tonnes
b) 20,000 tonnes d) 10,000
tonnes iv) What type of nodules generally
selected for isolation of effective rhizobia?
a) White-coloured c)
Pink-coloured b) Green-coloured
d) Blue-coloured
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ASSESSMENT
Model Answers i) Legumes ii) 50-200 kg
Nitrogen iii) 15,000 tonnes iv) Pink-coloured
nodules
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REFERENCES

• i) Soil Microbiology
  N. S.Subba Rao
• ii) Advances in Microbiology N.
  S.Subba Rao
• iii) Bio-fertilizer and Organic Farming NIIR
  Board
• iv) Nitrogen fixing organisms
• (Pure and applied aspects) J.
  I. Sprent and P. Sprent