A Brazilian Bacillus thuringiensis strain highly active to sugarcane borer Diatraea saccharalis (Lepidoptera: Crambidae)

Abstract

The control of the major sugarcane pest, Diatraea saccharalis, is limited by the stem location of the caterpillar. As part of a long-term project towards the development of an alternative and efficient delivery system of Cry proteins to control the sugarcane borer, the current work describes the selection and characterization of a Brazilian B. thuringiensis strain with prominent activity towards D. saccharalis. Strain S76 was eleven-fold more active than the HD-1 Lepidoptera-standard strain, as estimated by the LC50 of 13.06 µg/L and 143.88 µg/ L, respectively. We observed bipiramidal and cuboidal crystals similar to those found in other B. thuringiensis strains with entomopathogenic activity against Lepidoptera and Diptera. In addition, smaller and spherical crystalline inclusions were also observed. The plasmid profile of strain S76 is similar to that of HD-1. PCR amplifications of S76 DNA using cry specific primers confirmed the presence of cry1Aa, cry1Ab, cry1Ac, cry2Aa1, and cry2Ab2, but not cry1Ad, cry2Ac and cry9 type genes. No differences that could explain the superior activity of S76 when compared to HD-1, the Lepidoptera standard strain, were observed. Nevertheless, its higher entomopathogenic activity has pointed this strain S76 as a potential source of cry genes to control sugarcane borer, an important pest that affects sugarcane, a crop that occupies a planted area of about 6 million ha in Brazil.

Seleção e caracterização de estirpes de Bacillus thuringiensis eficientes contra a Diatraea saccharalis (Lepidoptera: Crambidae)

“…As estirpes tóxicas pertenciam aos sorotipos kurstaki (S1258, S1264, S2193 e S2195), tolworthi (S1303 e S1304), aizawai (S1295), galleriae (S1298) e morrissoni (S1301 Gitahy et al (2007). Dados semelhantes foram obtidos por Rosas-García (2006), com isolado de sorotipo kurstaki, que demonstrou atividade tóxica contra a broca-da-cana no México.…”

“…Destas, seis eram estirpes recombinantes de B. thuringiensis que produzem toxinas individuais Cry1Aa, Cry1Ab, Cry1Ac, Cry1B, Cry1I e Cry2Aa. As estirpes foram cultivadas em meio de cultura Embrapa, conforme Monnerat et al (2007), em incubador rotativo, Modelo 3595, a 200 rpm (Labline Instruments, Melrose Park, IL, EUA), a 28ºC durante 72 horas, até sua completa esporulação.…”

“…1794) (Lepidoptera: Crambidae), conhecida como broca-da-cana, é a que causa mais prejuízos à cultura. Seu hábito alimentar, que se caracteriza pela penetração da lagarta nos colmos da planta, limita seu controle por métodos convencionais (Gitahy et al, 2007). O controle desta praga, no entanto, tem sido realizado com agrotóxicos, apesar dos potenciais riscos desses produtos ao homem e ao ambiente.…”

“…O controle desta praga, no entanto, tem sido realizado com agrotóxicos, apesar dos potenciais riscos desses produtos ao homem e ao ambiente. Assim, agentes de controle biológico são uma alternativa ecológica e economicamente viável (Praça et al, 2004), e o uso de Bacillus thuringiensis é uma estratégia promissora no controle de D. saccharalis, conforme relatado por Praça et al (2004) e Gitahy et al(2007).…”

Structural and Functional Analysis of Giant Strong Component of Bacillus thuringiensis Metabolic Network

“…In this article, the use of metabolic reaction data to generate a metabolic network with 830 nodes and 1132 links of an important insecticidal bacterium B. thuringiensis (11,22) is achieved firstly. Subsequently, structural analysis of B. thuringiensis metabolic networks is explained and discussed based "bow tie" structure which is proposed by Ma and Zeng (24), emphasis is placed on the giant strong component (GSC) part.…”