Agriculture Reference
In-Depth Information
Classification of
Rhizobium
Bio-fertilizers
1.
Rhizobium
leguminosarum
2.
Biovarphaseoli
Phaseolus
(Bean)
3.
Biovarviceae Vicea
(Vetch)
4.
Biovartrifolii Trifolium
(Berseem)
5.
Rhizobium meliloti Melilotus
(Senji)
Rhizobium loti
6.
Bradyrhizobium japonicum Glycine
(Soybean)
7.
Bradyrhizobium species Lupinus
(Lupin),
Vigna, Cicer
Recently two more genera have been included in the family Rhizobiaceae. They are
Sinorhizobium
and
Azorhizobium
which are nodulating the Soybean and Dhaincha
(
Sesbania
)
,
respectively.
Azorhizobium
caulinodans
were isolated from the stem
nodules of
Sesbania rostrata
but can also colonise and produce nodules in rice
roots.
Azorhizobium caulinodans
also capable of fixing nitrogen in the free living
state (Mandon et al.
1998
).
Blue Green Algae (BGA)/Cyanobacteria
Blue-green algae or cyanobacteria are photosynthetic prokaryotes capable of fixing
nitrogen with the help of enzyme nitrogenase. They are generally aquatic, small
organisms visible as a single cell or large accumulation of cells (colonies) or strings
of cells i.e. trichomes under microscope, sometimes accumulations are so large that
they can be seen with a naked eye. Another name for blue-green algae is cyano-
phytes, cyanobacteria and most recently cyanoprokaryotes. As far as vegetative
structure is considered they are resemble algae and other free living bodies. Their
requirements for light, nutrients and carbon dioxide are similar. Certain types of
blue-green algae have tiny gas vesicles in their cells that help to regulate buoyancy
or get submerged under water in response to light fluctuations and availability of
nutrient. BGA include
Anabaena, Nostoc, Plectonema, Syctonema, Calothrix, Aulo-
sira, Tolypothrix
. Among these commercially available representatives are cultures
of
Anabaena, Nostoc, Tolyphorix and Aulosira
. The blue-green alga (
Anabaena
azollae
) shows a symbiotic association with
Azolla
(aquatic fern) and also fixes
atmospheric nitrogen. BGA has shown to be associated with the
Azolla
present in
ventral pore along the dorsal lobe of each vegetative leaf. This endophyte fixes at-
mospheric nitrogen and remains inside the tissue of the water fern in addition to its
use in utilization in paddy fields. BGA fixes atmospheric nitrogen in semi aquatic
ecosystem and takes part in photosynthetic activity.
Azolla
is a fast growing water
fern and has ability to double its weight within a week.
Azolla
being rich in organic
manure mineralizes the soil nitrogen rapidly and is made available to the plants. It
is a protein rich feed to fish and poultry. BGA besides nitrogen fixation also synthe-
sizes and releases growth stimulating substances viz., auxin and amino compounds
that enhance the growth of rice plants. Algae can be multiplied in the paddy field
by broadcasting the inoculants at the rate of about 10 kg/ha. It has been observed
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