Abstract

Jyotirmayee Das, Bandana Das and Tushar Kanti Dangar

Different microbial populations and Bacillus thuringiensis (Bt) diversity in saline soils of three rice fields and two fallow lands of coastal Orissa, India, were assessed. Populations (x105 colony forming units (cfu) g -1 dr. soil) of aerobic heterotrophic (4.5 - 47.6), spore-forming (1.00 - 21.2) and Gramnegative (0.8 - 27.8) bacteria were relatively more abundant in the soils than those of nitrifying (0.10 - 1.02), denitrifying (0.15 - 1.31), phosphate-solubilizing (1.4 - 8), sulfur-oxidizing (3.2 – 8.0) and asymbiotic nitrogen-fixing (2.6 – 4.0) bacteria. Populations of fungi (0 - 2) and actinomycetes (0 - 0.02) were low. Bt populations varied between 0.5 - 6.4 x 105 cfu g-1 dr. soil in the different fields. The Bt isolates (n = 406) could be divided into 9 groups (TB 155-161, 163, 164), based on their cultural, morphological and crystal (viz. bipyramidal, spherical and pleomorphic) characteristics. Phenotypically the isolates were similar to B. thuringiensis subsp. galleriae (TB155), kurstaki/kenyae/aizawai (TB156, 159, 164), darmstadiensis (TB158, 163), thompsoni/coreanensis (TB157) and entomocidus (TB161). However, one isolate (TB160) did not match with any subspecies.