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ISOLATION AND IDENTIFICATION OF NOVEL Bacillus thuringiensis Cry GENES WITH INSECTICIDAL ACTIVITY AGAINST Spodoptera litura AND Helicoverpa armigera THROUGH MOLECULAR APPROACHES

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Title ISOLATION AND IDENTIFICATION OF NOVEL Bacillus thuringiensis Cry GENES WITH INSECTICIDAL ACTIVITY AGAINST Spodoptera litura AND Helicoverpa armigera THROUGH MOLECULAR APPROACHES
 
Creator LALITHA, C
 
Contributor MURALI KRISHNA, T
 
Subject biological phenomena, animal developmental stages, genes, bacteria, land resources, land management, bacillus thuringiensis, pcr, proteins, sampling
Bacillus thuringiensis, Spodoptera litura , Helicoverpa armigera
 
Description Bacteria were isolated from total of 410 soil samples and 255 bacterial
infected silkworms. Isolated bacteria were subjected to gram staining and crystal
staining, and 120 crystal staining positive B.t. strains were identified. Maximum
number of crystal staining positive isolates were obtained from Southern Zone.
Mostly the B.t. strains with bipyramidal and cuboidal crystals were found to be
toxic against S. litura and H. armigera.
More than 50% mortality of all the three instars (I, II and III) of S. litura
was recorded with 32 B.t. strains (34.16% of total number of strains). The mean
per cent larval mortality of I, II and III instar S. litura was highest with the
isolate HD1 (85.56%) followed by B.t. strain 375 (80%) similarly for II and III
instar larvae of H. armigera (HD1 and 281).
Sixteen effective native B.t. strains (4, 12, 15, 21, 25, 32, 44, 83, 111,
139, 206, 281, 341, 375, 405 and 416) were assayed at five different dilutions
10-1 to 10-5 to determine LC50 by probit analysis. The reference strain HD1
registered the least LC50 and LC90 values in terms of CFU/1ml followed by
native strain 375.
Ninety six B.t. strains were amplified by using seven lepidopteran specific
primers (Cry 1F, Cry 2, Cry 8, Cry 9, Cry 20, Lep1 and Lep 2). More than two
genes were detected in 16 B.t. strains out of which B.t. strain 375 and 281 were
xvii
found promising in the control of S. litura and H. armigera, respectively. Four
genes Cry 2, Cry 8, Cry 9 and Lep 2 with cuboidal crystals were present in B.t.
strain 375, whereas Cry 1F, Cry 8, Cry 20 and Lep1 genes with bipyramidal
crystals were present in B.t. strain 281.
Among the four random primers used for RAPD (OPC-11, OPC-14,
OPD-8 and OPD-16) OPC-11 showed 92.3% polymorphism. B.t. strains 4, 12,
15, 21, 22, 25, 44, 49, 53, 58, 61, 67, 71, 77, 83, 91 revealed 100% genetic
variation with the B.t. strains 111, 122, 179, 206, 351, 375, 432 and 434.
Dendrogram constructed indicated 4 clusters and B.t. strain 206 formed a
separate distinct cluster.
Some effective B.t. strains were also characterized using 16S rDNA
sequences of B.t. strain 122 (GenBank accession number JN798214) and 375
(GenBank accession number JN798215) showed 100% similarity with those in
GenBank. Phylogenic dendrogram exhibited B.t. strain 122 as distinct cluster
compared to others, where as B.t. strain 375 was with same clade with
JF 521546 (isolated from Tirupati South India).
Field evaluation of B.t. strains (122 and 375) against H. armigera and
S. litura in Field bean and Groundnut, respectively indicated solid formulations
to be more effective than liquid formulations. Higher yields and low pod damage
was registered in solid formulations.
 
Date 2016-06-06T10:24:44Z
2016-06-06T10:24:44Z
2012
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/66807
 
Language en
 
Relation D9046;
 
Format application/pdf
 
Publisher ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY