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

Abstract

Resumo -O objetivo deste trabalho foi selecionar e caracterizar estirpes nativas de Bacillus thuringiensis tóxicas a Diatraea saccharalis (Lepidoptera: Crambidae). Cento e seis estirpes pertencentes ao Banco Selection and characterization of Bacillus thuringiensis efficient strains against Diatraea saccharalis (Lepidoptera: Crambidae)Abstract -The objective of this work was to select and characterize native strains of Bacillus thuringiensis toxic to Diatraea saccharalis (Lepidoptera: Crambidae). A hundred-and-six strains, belonging to the bank of invertebrate bacteria (Brazil), of Embrapa Genetic Resources and Biotechnology, were tested as to their toxicity to D. saccharalis, and the most toxic ones were characterized by biochemical and molecular methods. Out of the 106 tested strains, 16 caused 100% mortality within 24 hours. The three most toxic strains showed median lethal concentrations between 8 and 43 ng cm -2 . The protein profile of the 16 strains showed the presence of 130 and 65 kDa proteins, and the molecular characterization showed the presence of cry1and cry2 type genes: cry1Aa, cry1Ab, cry1Ac, and cry2Aa. The median lethal concentration of spores and crystals obtained from recombinant strains, which individually expressed the genes cry1Aa, cry1Ab, cry1Ac, and cry2Aa, varied between 222 and 610 ng cm -2 , values much higher than the ones of the most toxic native strains, which have the possibility of simultaneously expressing these genes. This result indicates a synergy between the toxins. There are interactions between B. thuringiensis toxins and their receptors in the sugarcane borer.

Rizobacteria in the control of pest insects in agriculture

“…Selecting and characterizing Brazilian strains of Bacillus thuringiensis toxic to P. xylostella, Praça (2012) found that the B. thuringiensis strains S1905 and S2122 caused 100% of mortality in caterpillars in the 3º instar of Plutella xylostella in evaluation performed 48 h after caterpillars had been exposed to selective bioassays, whereas S2124 caused 58.33% of mortality after the same period and 98.33% of mortality after 96 h. In these cases, CL 50 values ranged from 2.33 to 4.84 ng/mL, with results of toxicity similar to the control. Viana et al (2009) Recently, Macedo et al (2012), selecting and characterizing native strains of B. thuringiensis toxic to Diatraea saccharalis (Lepidoptera: Crambidae), observed that the strains causing more than 75% of mortality after dilution of 50 times were: S602, S1264 and S1301. From these strains, the most toxic to D. saccharalis were S602 and S1264, with statistically similar CL 50 values, but different from S1301.…”

Seleção de estirpes de Bacillus thuringiensis tóxicas à Helicoverpa armigera e promotoras de crescimento vegetal

“…, leguminosas (TANUJA et al, 2003), amendoim (WANG et al, 2014) e ainda como inseticida sistêmico (PRAÇA et al, 2012) pode vir a ser uma alternativa interessante.…”

“…(ARONSON et al, 1986 (SHISHIDO et al, 1999) e B. thuringiensis (MONNERAT et al, 2003;PRAÇA et al, 2012) e também promoveram o crescimento vegetal (GOMES et al, 2003;TANUJA et al, 2013;WANG et al, 2014).…”

“…Estirpes pertencentes ao sorotipo kurstaki são consideradas as mais tóxicas para insetos da ordem Lepidoptera (AZZOUZ et al, 2014), porém as estirpes pertencentes ao sorotipo morrisoni (MACEDO et al, 2012;APAYDIN et al, 2008), aizawai (SHOJAADDINI et al, 2012), sotto (GUERCHICOFF et al, 2001), fokuokaensis (MELATTI et al, 2005) e thuringiensis (JAQUET et al, 1987), também apresentam alta atividade inseticida contra insetos lepidópteros, corroborando os resultados encontrados neste trabalho.…”

“…Macedo et al (2012) (BRAVO et al, 2011 estirpes apresentaram apenas a proteína de 130 kDa e as S93, S608 e S1289 apresentaram apenas a proteína de 65 kDa.…”