Toxin Gene Contents and Activity of Bacillus thuringiensis Strains Against Two Sugarcane Borer Species, Diatraea saccharalis (F.) and D. flavipennella (Box)

Abstract

Bacillus thuringiensis (Berliner) bears essential characteristics in the control of insect pests, such as its unique mode of action, which confers specificity and selectivity. This study assessed cry gene contents from Bt strains and their entomotoxicity against Diatraea saccharalis (F.) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae). Bioassays with Bt strains were performed against neonates to evaluate their lethal and sublethal activities and were further analyzed by PCR, using primers to identify toxin genes. For D. saccharalis and D. flavipennella, 16 and 18 strains showed over 30% larval mortality in the 7th day, respectively. The LC values of strains for D. saccharalis varied from 0.08 × 10 (LIIT-0105) to 4104 × 10 (LIIT-2707) spores + crystals mL. For D. flavipennella, the LC values of strains varied from 0.40 × 10 (LIIT-2707) to 542 × 10 (LIIT-2109) spores + crystals mL. For the LIIT-0105 strain, which was the most toxic to D. saccharalis, the genes cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, cry8, and cry9C were detected, whereas for the strain LIIT-2707, which was the most toxic to D. flavipennella, detected genes were cry1Aa, cry1Ab, cry1Ac, cry1B, cry1D, cry1F, cry1I, cry2Aa, cry2Ab, and cry9. The toxicity data and toxin gene content in these strains of Bt suggest a great variability of activity with potential to be used in the development of novel biopesticides or as source of resistance genes that can be expressed in plants to control pests.

Development of a bioassay method to test activity of cry insecticidal proteins against Diatraea spp. (Lepidoptera: Crambidae) sugarcane stem borers

“…The efficacy of these insecticidal proteins is commonly evaluated in bioassays under controlled conditions with the purified protein incorporated in an artificial diet and monitoring survival and development [18], or by direct observation of their efficacy in plants in the field [19]. Several studies have assessed the activity of diverse Bt proteins, such as Cry1Ab, Cry1Ac, Cry1F, Cry2Ab, and Vip3Aa20, on sugarcane stem borers, including Diatraea saccharalis (F.), Diatraea flavipennella Box and Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) [15,17,[20][21][22][23]. These studies were facilitated by the availability of an artificial diet capable of sustaining D. saccharalis development and reproduction [24,25].…”

Caracterização do risco de infestação da broca da cana-de-açúcar no estado de São Paulo, com base em variáveis meteorológicas e técnicas de mineração de dados

“…Com isso, além da perda quantitativa de matéria prima ocasionada pela alimentação, essa praga favorece, também, a instalação de microrganismos como fungos e bactérias por meio dos orifícios que fazem ao penetrar nos colmos. Esses patógenos que atacam a cana em decorrência da infestação da broca afetam negativamente a qualidade dos produtos finais, como o açúcar e o etanol (DINARDO-MIRANDA, 2008;ROSSATO JÚNIOR et al, 2013) A forma de encontrar a praga é iniciar intensos levantamentos para avaliar a presença desta praga no campo buscando massa de ovos, larvas pequenas nas folhas e larvas grandes dentro do colmo, sendo a observação dos dois primeiros estágios bem mais trabalhosa (SILVA et al, 2018). Nesse contexto, o desenvolvimento de modelos matemáticos para D. saccharalis, capazes de prever a ocorrência deste inseto em campo e, portanto, indicar o momento exato para a realização do controle pode trazer um enorme benefício.…”