Field Evaluation of Soybean Engineered with a Synthetic <I>cry1Ac</I> Transgene for Resistance to Corn Earworm, Soybean Looper, Velvetbean Caterpillar (Lepidoptera: Noctuidae), and Lesser Cornstalk Borer (Lepidoptera: Pyralidae)

Abstract

A transgenic line of the soybean 'Jack', Glycine max (L.) Merrill, expressing a synthetic cry1Ac gene from Bacillus thuringiensis variety kurstaki (Jack-Bt), was evaluated for resistance to four lepidopteran pests in the field. Jack-Bt and genotypes serving as susceptible and resistant controls were planted in field cages and artificially infested with larvae of corn earworm, Helicoverpa zea (Boddie), and velvetbean caterpillar, Anticarsia gemmatalis (Hübner), in 1996, 1997, and 1998, and also with soybean looper, Pseudoplusia includens (Walker), in 1996. Susceptible controls included Jack (1996-1998), 'Cobb' (1996), and Jack-HPH (1996). GatIR 81-296 was used as the resistant control in all 3 yr. Compared with untransformed Jack, Jack-Bt showed three to five times less defoliation from corn earworm and eight to nine times less damage from velvetbean caterpillar. Defoliation of GatIR 81-296 was intermediate between that of Jack and Jack-Bt for corn earworm, and similar to that of Jack for velveltbean caterpillar. Jack-Bt exhibited significant, but lower resistance to soybean looper. Jack-Bt also showed four times greater resistance than Jack to natural infestations of lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), in conventional field plots at two locations in 1998. Data from these experiments suggest that expression of this cry1Ac construct in soybean should provide adequate levels of resistance to several lepidopteran pests under field conditions.

Interação de proteínas Cry1 e Vip3A de Bacillus thuringiensis para controle de lepidópteros-praga

“…Embora tenha-se destacado das demais proteínas, Cry1Ac foi mais efetiva para A. gemmatalis do que para C. includens. Estudos realizados com uma linhagem transgênica de soja, que expressava altos níveis de proteína a partir do gene cry1Ac, relataram mortalidade total em lagartas de A. gemmatalis e redução significativa da população de C. includens, em ensaios de suscetibilidade e de alimentação realizados em laboratório (Stewart Junior et al, 1996) e no campo (Walker et al, 2000).…”

“…Walker et al (2000) relataram que uma linhagem transgênica de soja com altos níveis de proteína a partir do gene sintético cry1Ac ocasionou mortalidade total em larvas de A. gemmatalis e redução significativa da população de C. includens, em ensaios de suscetibilidade e de alimentação realizados em laboratório e no campo.…”

Agronomic performance, chromosomal stability and resistance to velvetbean caterpillar of transgenic soybean expressing cry1Ac gene

“…A transgenic line of soybean Jack cultivar, expressing a synthetic cry1Ac gene, caused complete A. gemmatalis larval mortality, in laboratory bioassays (Stewart Junior et al, 1996) and in artificially infested field cages (Walker et al, 2000). More recently, transgenic lines of soybean (A5547), expressing a synthetic cry1A gene, were evaluated for the resistance against several lepidopteran pests in screenhouse and in conventional field trials, in which Bt lines exhibited virtually complete efficacy against all pests tested (Macrae et al, 2005).…”

“…This insect causes extremely high levels of defoliation, when infestation is heavy, and can severely damage axillary meristems. A single larva can consume up to 110 cm 2 of soybean foliage (Walker et al, 2000). Consequently, expensive insecticide application or control measures are necessary to prevent yield losses in regions with high occurrence of A. gemmatalis (Macrae et al, 2005;Miklos et al, 2007).…”

“…B. thuringiensis has long been used for controlling insect pests as a biological insecticide. The activity of delta-endotoxin from B. thuringiensis in controlling the larvae of A. gemmatalis has been described (Stewart Junior et al, 1996;Walker et al, 2000;Macrae et al, 2005;Miklos et al, 2007).…”