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Activity and molecular characterization of Bacillus thuringiensis (Berliner) isolates to the sugarcane borers Diatraea saccharalis (Fabr.) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae).

By Liliane Marques da Silva

Abstract

A bactéria Bacillus thuringiensis (Berliner) apresenta características essenciais no controle de insetos-praga, tais como seu modo de ação, especificidade e seletividade. Dessa forma, esta pesquisa objetivou avaliar a atividade tóxica de isolados de B. thuringiensis em larvas de Diatraea saccharalis (Fabr.) e Diatraea flavipennella (Box) e caracterizar quanto à presença de gene de toxinas os isolados tóxicos. Estas pragas foram mantidas em dieta artificial. Foram utilizados 24 isolados, preservados em meio LB, glicerol a 15% e SDS a 0,02% e mantidos a -80C. Para caracterização molecular foram utilizados iniciadores gerais e específicos. Nos testes de patogenicidade com D. saccharalis e D. flavipennella, 16 e 18 isolados mostraram-se ativos, respectivamente. Os valores de CL50 entre os isolados para a população de D. saccharalis variaram entre 0,08 x 105 (LIIT-0105) e 4104 x 105 (LIIT-2707) esporos + cristais/mL. O isolado LIIT-0105 foi 18,59 e 4382 vezes mais tóxico que o Btk e Btt, respectivamente. Para D. flavipennella, os valores de CL50 entre os isolados variaram entre 0,40 x 105 (LIIT-2707) e 542,75 x 105 (LIIT-2109) esporos + cristais/mL. O isolado LIIT-2707 foi 11,52 e 1137 vezes mais tóxico que o Btk e Btt, respectivamente. O isolado LIIT-0105 que teve a menor CL50 para D. saccharalis apresentou os genes cry1, cry2, cry8, cry9, cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry1I, cry2A, cry2Aa1, cry2Ab2 e cry9C e para D. flavipennella o isolado LIIT-2707 apresentou a menor CL50 amplificando para os genes cry1, cry2, cry9, cry1Aa, cry1Ab, cry1Ac, cry1B, cry1D, cry1F, cry1I, cry2A, cry2Aa1 e cry2Ab2. Os resultados sugerem que isolados de B. thuringiensis apresentam grande potencial e variabilidade para bioprospecção desta bactéria, para o desenvolvimento de produtos ou transformação de plantas que expressem genes de Bt para o controle de D. saccharalis e D. flavipennella.The bacterium Bacillus thuringiensis (Berliner) presents remarkable aspects for the control of insect pests, such as its mode of action, specificity and selectivity. Thus, this study aimed to evaluate the toxic activity of B. thuringiensis isolates in larvae of Diatraea saccharalis (Fabr.) and Diatraea flavipennella (Box) and determine the toxin gene contents for the very active isolates. The insects were maintained on artificial diet. Twenty four isolates were used, which were preserved in LB medium, 15% glycerol and 0.02% SDS and kept at -80 C. General and specific primers were used to survey for toxin genes. In pathogenicity tests with D. saccharalis and D. flavipennella, 16 and 18 isolates showed activity toward borers, respectively. The LC50 values among isolates for the population of D. saccharalis ranged from 0.08 x 105 (LIIT-0105) and 4104 x 105 (LIIT-2707) crystals + spores/mL. The isolated LIIT-0105 was 4,382 and 18.59 times more toxic than Btk and Btt, respectively. For D. flavipennella, the LC50 values between isolates ranged from 0.40 x 105 (LIIT-2707) and 542.75 x 105 (LIIT-2109) crystals + spores/mL. The isolate LIIT-2707 was 1,137 and 11.52 times more toxic than Btk and Btt, respectively. The isolate LIIT-0105 presented the lowest LC50 for D. saccharalis that harbored the genes cry1, cry2, cry8 cry9, cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry1I, cry2A, cry2Aa1, cry2Ab2, cry9C. For the borer D. flavipennella, the isolated LIIT-2707 presented the lowest LC50 and the following genes cry1, cry2, cry9, cry1Aa, cry1Ab, cry1Ac, cry1B, cry1D, cry1F, cry1I, cry2A, cry2Aa1 and cry2Ab2 were amplified. The results suggest that B. thuringiensis isolates present a great variability of genes for bioprospection, and thus potential for developing new products and insertion on plants to express Bt genes for the control of D. saccharalis and D. flavipennella

Topics: Broca da cana-de-açúcar, Lepidoptera, Inseto, Bactéria, Patogenicidade, Bioinseticida, ENTOMOLOGIA AGRICOLA, Bioinsecticide, Pathogenicity, Insect, Sugarcane borer, ENTOMOLOGIA AGRICOLA
Publisher: Universidade Federal Rural de Pernambuco
Year: 2013
OAI identifier: oai:agregador.ibict.br.BDTD_UFRPE:oai:tede.ufrpe.br:1713
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