Page 335 - e-Book

The several crop fields, like sugarcane, jowar, wheat, cotton, onion and fallow lands were

marked out for collection of soil.
Isolation of blue-green algae

For isolation and study of soil microflora particularly blue-green algae in the collected soil
samples, the BG- 11 (Rippka et al., 1979) and Fogg’s (Fogg, 1942, 1949; Jacobson, 1951)

culture media used. Two different sets were prepared; one set was used with 100 ml of
modified Fogg’s medium and the second with 100 ml of BG-11 medium. These were then

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sterilized for 20 minutes at 121 C and 15 lbs pressure.
For isolation and identification of blue-green algal forms, 5 gm of soil samples were
inoculated in sterilized flasks having 100 ml of BG-11 and Fogg’s media separately.

Inoculation was done in front of laminar airflow unit and inoculated flasks were incubated at

0
28  2 C under 2.5 K lux fluorescent light for 2- 3 weeks under 16/ 8 hours light / dark
cycles. The visible growth of blue-green algae appeared in the enrichment cultures after 20-

25 days period of incubation.

Taxonomical studies
Slides were prepared for the taxonomical studies by using pure glycerin. These were

observed under Olympus binocular, CH 20i research microscope. Microphotographs were
taken by using computer attached CCD camera with Aver capture software and SONY

Cybershot camera. Morphometric studies were carried out by using ocular and stage
micrometers. Microphotography and measurements of the species were made by ocular and

10X, 40X, 100X objectives with 10X and 15X eyepieces.

Identification of the isolated taxa
The taxonomic identification was done by following the monographs and keys given

by Prescott (1951), Desikachary (1959) and Anand (1990). The identified taxa were arranged
according to the system of classification given by Desikachary (1959).

Relative abundance of blue-green algae
The relative abundance of a Cyanophycean algal form was calculated (Nayak et al.,

2001) by using the following formula:

Y
Relative Abundance = X 100
X

Where, X= Total number of soil samples collected.

Y= Number of soil samples harbouring the alga.

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