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Bt Research 2015, Vol.6 No.1 1-8
ISSN 1925-1939
http://bt.biopublisher.ca
1
Research Article Open Access
Selection of
B. thuringiensis
strains containing genes effective in the control of
Spodoptera frugiperda
.
Ana Rita N. Lemes , Suzana C. Marucci, Juliana R. V. Costa, Eliane C. C. Alves, Odair A. Fernandes, Manoel
Victor F. Lemos and Janete A. Desidério
Univ Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, 14884-900, Jaboticabal, São Paulo, Brazil
Corresponding author email
Bt Research, 2015, Vol.6, No.1 doi: 10.5376/bt.2015.06.0001
Received: 24 Oct., 2014
Accepted: 29 Jan., 2015
Published: 31 Jan., 2015
© 2015
Ana Rita N. Lemes et al., 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:
Ana Rita N. Lemes et al., 2015,
Selection of
B. thuringiensis
strains containing genes effective in the control of
Spodoptera frugiperda
.
,
Bt
Research, Vol.6, No.1, 1-8
(doi
Abstract
The bacterium
Bacillus thuringiensis
(Berliner) is an important entomopathogen that can replace chemical pesticides in
crops. In addition to the endotoxins found in
B. thuringiensis
, new proteins have been studied recently, such as Vip and Chitinase,
which can enhance toxic effects by acting synergistically. Thus, the objectives of this work were to select new
B. thuringiensis
isolates carrying
cry1Fa, vip3Aa
,
and
chi
; to verify polymorphisms based on PCR-RFLP analysis; and to evaluate mortality and
existence of synergistic effects of these genes on
Spodoptera frugiperda
larvae. A total of 114 isolates were subjected to screening via
PCR to detect the
vip3Aa
,
cry1Fa
, and
chi
genes
.
Neonatal larvae of
S. frugiperda
were bioassayed using isolates containing one, two
or all three genes and were compared to the standard strains
.
The PCR-RFLP analysis showed the absence of polymorphisms in these
gene regions. The
B. thuringiensis
isolates from different regions of Brazil contained different combinations of the
cry1Fa, vip3Aa
,
and
chi
genes. The presence of
vip3Aa
appeared to act synergistically with
chi
, and the combination of all three genes caused
increased mortality in
S. frugiperda
larvae. Due to their insecticidal potential, these isolates are a prospective source of genes that can
be used to genetically modify crops to increase the efficacy of pest control.
Keywords
Biological control; Vip3Aa; Cry1Fa; chitinase
Background
Cases of resistance to
Bacillus thuringiensis
Berliner
endotoxins among insect populations have been
reported as a result from selection under laboratory
and field conditions. In cases where resistance has
evolved, the insects have shown mutations in genes
encoding proteins involved in various stages of the
mode of action (Heckel et al., 2007; Tabashnik et al.,
2009). In contrast to the variety of resistance
mechanisms found in strains of insects selected in the
laboratory, only one important mechanism of
insecticide resistance, the alteration of binding sites,
has been detected in insects that have evolved
resistance under field or greenhouse conditions (Ferré
and Van Rie 2002; Wang et al., 2007; Tabashnik et al.,
2011). Thus, searching for new families of insecticidal
toxins that present different modes of action compared
to that of the Cry proteins, which are broadly used in
the biological control of insects, is a strategy that has
been employed to circumvent and/or delay the
development of resistance. The discovery of new
B.
thuringiensis
genes is crucial to develop new
bioinsecticides and to provide a source of different
genes for constructing genetically modified plants.
In the case of Bt maize, which contains the
cry1Fa
gene and is currently commercially available to
control
Spodoptera frugiperda
(J. E. Smith)
(Lepidoptera: Noctuidae), new genes associated to
cry1Fa
gene could be utilized with the aim of
obtaining pyramidized maize plants to manage the
development of resistance to Bt maize in
S. frugiperda
populations. One new insecticidal protein family that
could be employed is Vip3A, which was first
described by Estruch et al. (1996). The genes
encoding this protein family exhibit a high specificity
for lepidopterous insects and are highly active against
these insects; therefore, they are considered alternative