Screening Of Bt Insecticidal Proteins With High Activity And The Synergistic Combinations Against Lymantria Dispar (Linnaeus) Larvae

Lymantria dispar (Linnaeus) is an important agricultural and forestry pest in the world. With the aim of identifying Bt proteins and their synergistic combinations that would be useful in the management of Lymantria dispar.Eleven Bt proteins from Bt were extracted to test their toxicity against 3-day-old larvae of L. dispar. Cry1Ac, Cry2Ab, Cry1Ca and Vip3Aj had highly insecticidal activity in the primary screen. The further bioassay showed that the toxicity of Cry1 Ac was the highest among the four proteins with LC50 of 2.47 μg/g. Cry2Ab and Cry1Ca had a higher insecticidal activity with the LC50 of 29.19 μg/g and 42.45 μg/g respectively. The novel protein of Vip3Aj were found having pesticidal activity for the first time with the LC50 of 101.26μg/g.The larvicidal activities of four combinations (1:1 ratios) of toxins (CrylAc+Cry2Ab, CrylAc+Cry1Ca, CrylAc+Vip3Aj, Cry2Ab+Cry1Ca) were evaluated against L. dispar. The results showed that LC50 of CrylAc+Cry2Ab combination was 0.64 μg/g, and the synergistic coefficient was highest among them with 7.098, suggesting a strong synergism. The synergistic coefficients for CrylAc+CrylCa and CrylAc+Vip3Aj combinations with LC50 of 0.76 μg/g and 1.06 μg/g, were 6.162 and 4.539 respectively, which also exhibited synergistic effect.