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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #86861
Title: EVALUATION OF TRANSGENIC SWEET CORN HYBRIDS EXPRESSING CRYIA(B) TOXIN FOR RESISTANCE TO CORN EARWORM AND FALL ARMYWORM (LEPIDOPTERA: NOCTUIDAE)

Author
item Lynch, Robert
item Wiseman, Billy
item PLAISTED, D. - NOVARTIS SEEDS, INC.
item WARNICK, D. - NOVARTIS SEEDS, INC.

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Bt is bacterium that produces a crystalline protein that is toxic to insec especially larvae of moths and butterflies. Genetic engineers have transferred a gene for the toxin to plants to control larvae that feed on plant foliage. We transferred a modified Bt-gene to peanut and evaluated plants containing this gene for presence of the toxin. The gene was transferred to peanut by shooting a small piece of the DNA containing the gene, the CRYIA(c) gene, into peanut tissue. Plants grown from the tissue and checked for expression of the toxic protein via immunoassay showed tha up to 0.18% of the total leaf protein was Bt protein. Feeding studies wit the lesser cornstalk borer larvae, a major pest of peanut in the US, showe up to 100% larval mortality and up to a 66% reduction in larval weight for larvae feeding on leaves from regenerated plants. Significant negative correlations were recorded between Bt protein in peanut leaves and surviva a and weight of lesser cornstalk borer larvae. Based on these results, transformed peanut containing the Bt gene may be effective in protecting plants from damage by larvae of the lesser cornstalk borer and other insec susceptible to the toxin produced by this Bt gene.

Technical Abstract: Since many of the lepidopterous insects which attack sweet corn, Zea mays L., are susceptible to insecticidal proteins produced by Bacillus thuringiensis ssp. kurstaki (Berliner)(Btk), transgenic sweet corn producing a Cry protein toxic to larvae of the major lepidopterous pests could reduce the quantity of insecticide currently used to provide injury free ears for both the fresh and processing sweet corn markets. Eight transgenic sweet corn hybrids containing a synthetic gene for CryIA(b) protein production were evaluated for resistance to the corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith). Isogenic non-Btk hybrids and resistant and susceptible controls were also evaluated. Laboratory tests revealed that all Btk sweet corn hybrids were highly resistant to leaf and silk feeding corn earworm larvae. Similarly, ear damage due to corn earworm was negligible in the field. With the exception of Btk 95-0901, the other Btk sweet corn hybrids were moderately resistant to leaf and silk feeding by the fall armyworm. The resistance to fall armyworm was expressed as significantly lower survival of neonates and significantly slower weight gain for 3- and 6-day-old larvae when fed excised whorl leaves of the Btk plants. Btk sweet corn hybrids appear ideal candidates to use in IPM programs for both the fresh and processing sweet corn markets and should drastically reduce the quantity of insecticides currently used to control these pest insects. Moreover, due to the phenology of sweet corn harvest and the toxicity of the Cry protein expressed in Novartis Btk sweet corn, it is highly unlikely that Btk sweet corn will contribute to the development of resistance in insects to Btk proteins.