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Bt Research 2013, Vol.4, No.1, 1
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7
ISSN 1925-1939
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1
Research Report Open Access
Selection of Brazilian
Bacillus thuringiensis
Strains for Controlling Diamondback
Moth on Cabbage in a Systemic Way
Lílian Botelho Praça , Carla Ferreira Caixeta , Ana Cristina Menezes Mendes Gomes , Rose Gomes
Monnerat
Embrapa Recursos Genéticos e Biotecnologia, Parque Estação Biológica - PqEB - Av. W5 Norte (final)Caixa Postal 02372, 70770-917, Brasília, DF , Brasil
Corresponding author email:
rose.monnerat@embrapa.br;
Authors
Bt Research, 2013, Vol.4, No.1 doi: 10.5376/bt.2013.04.0001
Received: 23 Jan., 2013
Accepted: 07 Feb., 2013
Published: 20 Mar., 2013
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Preferred citation for this article:
Praça et al., 2013, Selection of Brazilian
Bacillus thuringiensis
Strains for Controlling Diamondback Moth on Cabbage in a Systemic Way, Bt Research, Vol.4,
No.1 1-7 (doi: 10.5376/bt.2013.04.0001)
Abstract
Plutella xylostella
(L.) (Lepidoptera: Plutellidae) is a pest of great economic importance, due to losses caused in brassica
crops worldwide. The control of this pest is hindered by the selection of insects resistant to various chemicals and by its cryptic habit.
The aim of this work was to select a new
B. thuringiensis
strain with potential to control this insect pest in a systemic way because of
its cryptic habit between the leaves of the cabbage, as a new control strategy. The strains were characterized by morphological,
entomophatogenic, biochemical and molecular methods. No significant differences were observed in the CL
50
values of S1905,
S2122 and S2124 strains when compared to
Btk
HD-1 standard. The strains S1905 and S2124 had presented two main proteins with
130 kDa and 65 kDa, while S2122 presented only 130 kDa protein. The strains presented PCR products with expected sizes for
detection of some genes
cry1
and
cry2
and bipyramidal, spherical, and cuboidal crystals. The strains show some different
cry1
genes
that it’s very important to develop new products with different toxins to be used in management of
P. xylostella
resistance to
B.
thuringiensis
products and as a systemic bioinsecticide.
Keywords
Plutella xylostella
; Biological control; Toxicity;
cry
genes
Introduction
Plutella xylostella
L. (Lepidoptera: Plutellidae),
Diamondback Moth, is a pest that causes serious
damages in plants of Brassicaceae family, particularly
in cabbage culture (
Brassica oleraceae
var.
capitata
)
(Castelo Branco et al., 1996; França and Medeiros,
1998) in Brazil and other countries. The damage in the
production is around 60% (Imenes et al., 2002).
In the central region of Brazil, the attack of
P.
xylostella
in the field occurs along the year, although
its biggest occurrence is from July till September. The
critical period of attack occurs from the fourth till
seventh week after transplant, and either in the head
formation (Castelo Branco et al., 2003).
The main method of its control is the use of chemical
insecticides. There are a lot of reports showing four
insecticide applications per week increasing the
control cost and creating the potential for insect
resistance, principally where the cultivation is
uninterrupted (Villas Boas et al., 2004). This indicates
the necessity of reducing the consuming of
insecticides and the importance of using safe
alternatives of control.
The use of entomopathogenic bacteria
Bacillus
thuringiensis
(
Bt
) is a very important alternative for
insect control. During the sporulation process,
B.
thuringiensis
produces one or more proteins that are
toxic to diamondback moth that are specific,
innocuous to mammals, vertebrates and plants, and are
not toxic to environment (Monnerat et al., 1999;
Broderick et al
.,
2006).
The Laboratory of Entomopathogenic Bacteria at
Embrapa Genetic Resources and Biotechnology has
been studying, since 2003, a new way of controlling
P.
xylostella
using
B. thuringiensis
in its endophytic
form, in order to protect cabbage crops and other
brassicas from this important endophagous pest
(Monnerat et al., 2003; 2009).
The aim of this present study was to select and
characterize new
Bt
strains toxic to
P. xylostella
to be
used as a systemic bioinsecticide.