DEVELOPMENT AND CHARACTERIZATION OF SPORELESS MUTANTS OF LOCAL B.thuringiensis ISOLATES
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Date
2000
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University of Agricultural Science, Dharwad
Abstract
"The focus of the present study was to isolate Bacillus turingiensis
from soils of Western Ghat region in Uttar Kannada district of Karnataka,
characterization of their insecticidal activity and development of sporeless
mutants. Out of 32 Bacillus isolates, only eleven had endospores and
crystals. Two isolates M3 and M7 were toxic to diamond back moth
(Plutella xylostella) and Spodoptera litura causing 98.2 % and 97.4 %
mortality, respectively.
Isolates, M3 and M7 were subjected to MNNG mutagenesis for
developing sporeless mutants. Sporeless mutants, Mut M3 and Mut M7 were
obtained from M3 and M7 strains, respectively. Both mutants and wild type
isolates were characterized for intrinsic antibiotic resistance, insecticidal
activity, protein and plasmid profile. All the isolates including mutants were
sensitive to tetracycline, chloramphenicol and kanamycin. Both the mutants
were resistant to streptomycin but sensitive to nalidixic acid. On the other
hand wild type strains were resistant to nalidixic acid, but sensitive to
streptomycin. SDS-PAGE protein profile indicated the presence of Cry
protein bands of more than 130 kda and 65 kda in M3, M7 and Mut M3. But
Mut M7 had 67kda band The genetic distance (%) based on protein profile
was 50.00 per cent between Mut M3 and M7 and the maximum of 86.667 per
cent between Mut M3 and M3. All the isolates had a single plasmid of about
15kb. Toxicity of both wild type and mutant strain was tested against
nematode. All of them were found to be toxic to nematode. However PCR
with nematode specific primer did not yield any amplification product.
Talc and starch based wettable powder (WP) formulations of mutants
and wild type strains were tested against Spodoplera litura. Among talc and
starch based formulations talc based formulation was found to be more
effective and it was at par with the aqueous formulation of commercial
preparation ( Dipel 8L)"
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No. of references 96