Insecticidal Activity of 11 Bt toxins and 3 Transgenic Maize Events Expressing Vip3Aa19 to Black Cutworm, Agrotis ipsilon (Hufnagel)

Abstract

Black cutworm (BCW), Agrotis ipsilon (Hufnagel), is an occasional pest of maize that can cause considerable economic loss and injury to corn seedlings. This research mainly assessed the susceptibility of BCW neonates to 11 Bt toxins (Cry1Ab, Cry1Ac, Cry1Ah, Cry1F, Cry1Ie, Cry1B, Cry2Aa, Vip3_ch1, Vip3_ch4, Vip3Ca2, Vip3Aa19) by exposing neonates to an artificial diet containing Bt toxins and evaluated the efficacy of three transgenic maize events (C008, C009, C010) expressing Vip3Aa19 toxin against BCW. The toxin-diet bioassay data indicated that Vip3Aa19 protein (LC50 = 0.43 μg/g) was the most active against BCW. Chimeric protein Vip3_ch1 (LC50 = 5.53 μg/g), Cry1F (LC50 = 83.62 μg/g) and Cry1Ac (LC50 = 184.77 μg/g) were less toxic. BCW was very tolerant to the other Bt toxins tested, with LC50 values more than 200 μg/g. Greenhouse studies were conducted with artificial infestations at the whorl stage by placing second-instar BCW larvae into whorl leaf and the fourth-instar larvae at the base of maize seedings. These results suggest that these transgenic maize events expressing Vip3Aa19 can provide effective control for BCW.

Current Insights on Vegetative Insecticidal Proteins (Vip) as Next Generation Pest Killers

“…The Vip3Ba1 gene, isolated from Australian Bt isolates, was transformed and expressed in cowpea to provide protection against legume pod borer (M. vitrata), by strongly inhibiting larvae growth [93]. Similarly, a transgenic corn event (C008 and C010) expressing Vip3Aa19 has been found to be highly toxic against black cut worm [94]. When a tobacco plant was transformed with the N-terminal deletion mutant of the Vip3BR protein (Ndv200), it acquired full protection against S. littoralis, A. ipsilon, and H. armigera [95].…”

Vegetative Insecticidal Protein (Vip): A Potential Contender From Bacillus thuringiensis for Efficient Management of Various Detrimental Agricultural Pests

“…Recently, Vip3Aa19 protein was found to be very effective against A. ipsilon attack in maize with LC 50 value of 0.43 µg/g as compared to chimeric protein Vip3_Ch1 (5.53 µg/g). The LC 50 values were higher for Cry1Ac (184.77 µg/g) and Cry1F (83.62 µg/g), which indicates the better toxicity potential of Vip3 proteins as compared with the latter for this insect (Yan et al, 2020). Various modified and chimeric Vip3A proteins, either alone and in combination with crystalline proteins, developed and tested for their insecticidal activity have been described in Table 3.…”

Identification and Functional Characterization of Two Chitin Synthases in the Black Cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

“…The A. ipsilon colony was originally collected from the cornfields at Xinzhou, Shanxi province in 2013, and has been maintained in the laboratory for over 80 generations (Yan et al 2020). Larvae were provisioned with the artificial diet in a culture dish, and kept at 25 ± 1°C, 60 ± 5% RH, and a photoperiod of 16: 8 (L:D) h (Gu et al 2013).…”