Field evaluation of soybean engineered with a synthetic cry1Ac transgene for resistance to corn earworm, soybean looper, velvetbean caterpillar (Lepidoptera : Noctuidae), and lesser cornstalk borer (Lepidoptera : Pyralidae)

A transgenic line of the soybean 'Jack', Glycine max (L.) Merrill, expressi ng a synthetic cry1Ac gene from Bacillus thuringiensis variety kurstaki (Ja ck-Bt), was evaluated for resistance to four lepidopteran pests in the fiel d. Jack-Bt and genotypes serving as susceptible and resistant controls were planted in field cages and artificially infested with larvae of corn earwo rm, Helicoverpa zea (Boddie), and velvetbean caterpillar, Anticarsia gemmat alis (Hubner), in 1996, 1997, and 1998, and also with soybean looper, Pseud oplusia includens (Walker), in 1996. Susceptible controls included Jack (19 96-1998), 'Cobb' (1996), and Jack-MPH (1996). GatIR 81-296 was used as the resistant control in all 3 yr. Compared with untransformed Jack Jack-Bt sho wed three to five times less defoliation from corn earworm and eight to nin e times less damage from velvetbean caterpillar. Defoliation of GatIR 81-29 6 was intermediate between that of Jack and Jack-Bt for corn earworm, and s imilar to that of Jack for velveltbean caterpillar. Jack-Bt exhibited signi ficant, but lower resistance to soybean looper. Jack-Bt also showed four ti mes greater resistance than Jack to natural infestations of lesser cornstal k 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 resis tance to several lepidopteran pests under field conditions.