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Bt Research 2013, Vol.4, No.1, 1
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ISSN 1925-1939
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3
Table 3 Protein profile,
cry
genes and types of crystal present in
B. thuringiensis
strains
Figure 3 Transmission of electronic microscopy of
spores-crystals mixtures of
B. thuringiensis
strains
Note: A - S1450 (25000x), B - S1905 (30000x), C - S2122
(12000x) and D - S2124 (30000x), cb – bipyramidal crystal, ep
- spore, ce - spherical crystal and cc - cuboidal crystal
with Btk HD-1 standard. Although with 96 hours,
these strains didn’t present significative differences in
the mortality. These results were similar to others
researches with
B. thuringiensis
for the control of
P.
xylostella
that showed high toxicity (Medeiros
et al
.,
2005, Monnerat et al., 2007, Viana et al., 2009, Xie
et al., 2010).
The three strains S1905, S2122, S2124 exhibited LC
50
values similar to the standard strain Btk HD-1. All of
them presented a high toxicity against
P. xylostella
showed results similar to the others previously
described (Monnerat et al., 2007).
The result of protein profile showed in SDS-PAGE is
typical to lepidopteran active crystal protein from the
Cry1 and Cry2 classes (Schenpf et al., 1998, Praça et
al., 2004
)
and it is consistent with the results of the
bioassays presented in this work.
In the cause of
cry
genes
,
the three strains produced
PCR amplicons for
cry1
and
cry2
genes that are
effective for lepidopteran pests. The strain S1905
presented six
cry
genes like
Btk
HD-1 and S997
strains that were toxic to
Spodoptera frugiperda
and
Anticarsia gemmatalis
(Praça et al., 2004). The strains
S2122 presented seven genes and three of them
(
cry1Ab, cry1C
and
cry1D)
presented in
this strain
showed a similarity to
B. thuringiensis aizawai
, a
standard strains toxic to
P. xylostella
.
The strain S2122
and S2124 present
cry1E
and
cryF
genes respectively
and i
t is important to comment that these genes were
less abundant. Some researchers say that they are
found in the rains tropic (Bravo et al., 1998).
The genes
cry1C
and
cry1D
present in S2122 encoded
toxins active against
S. frugiperda
and
S.
exigua
(Bravo et al., 1998, Monnerat et al., 2006). All the
strains presented
cry2A
genes that encoded proteins
toxic to lepidopteran and dipteran species (Cárdenas et
al., 2001). The genes that were found most commonly
in the strains reported here were
cry1Ab
and
cry2Ab.
The presence of
cry1
and
cry2
genes in S1905 and
S2124 strains was consistent with their production of
the above proteins of 130 and 65 kDa (Figure 1),
respectively.
Strains
Profile perfil (kDa)
Genes
cry
Types of Crystal
HD-1-Btk S1450
130 – 65
cry1Aa, cry1Ab, cry1Ac, cry1B e
cry2Aa
and
cry2Ab
Bipyramidal, spherical and cuboidal
S1905
130 – 65
cry1Aa, cry1Ab, cry1Ac, cry1B,
cry2Aa
and
cry2Ab
Bipyramidal, spherical and cuboidal
S2122
130
cry1Aa, cry1Ab, cry1Ad, cry1Ce,
cry1D, cry1F
, and
cry2Ab
Bipyramidal, spherical and cuboidal
S2124
130 – 65
cry1Aa, cry1E cry2Aa
and
cry2Ab
Bipyramidal, spherical and cuboidal