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United States Department of Agriculture

Agricultural Research Service

Title: Nucotn33b and Delta and Pineland Cottons: Pink Bollworm (Lepidoptera: Gelechiidae) Infestations and Cry1ac Toxic Protein in Overwintered and Seeded Cottons with Bioassay Mortalities of Other Lepidopterous Larvae

Authors
item Henneberry, Thomas
item JECH, LYNN
item DE LA TORRE, THERESA

Submitted to: Southwest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2003
Publication Date: December 1, 2003
Citation: HENNEBERRY, T.J., JECH, L.J., DE LA TORRE, T.M. NUCOTN33B AND DELTA AND PINELAND COTTONS: PINK BOLLWORM (LEPIDOPTERA: GELECHIIDAE) INFESTATIONS AND CRY1AC TOXIC PROTEIN IN OVERWINTERED AND SEEDED COTTONS WITH BIOASSAY MORTALITIES OF OTHER LEPIDOPTEROUS LARVAE. SOUTHWEST ENTOMOLOGY. 2003. pp. 281-292.

Interpretive Summary: Transgenic (Bt) cottons have given outstanding control of lepidopterous insects in cotton. Resistance to Bt cotton is a concern and continuing research to fully understand Bt cotton ecosystems is essential. Bt and non-Bt DPL 5415 cottons were grown in furrow and furrow plus drip irrigated cotton plots in Arizona. The toxic protein produced in Bt cotton was measured using a commercially available method. Irrigation type had no effect on the toxic protein measured in cotton leaves or bolls. Early stage, laboratory-reared pink bollworm (PBW) larvae placed on Bt cotton bolls collected in field throughout the season died (100%) irrespective of decreasing amounts of measured toxic protein levels in late season bolls. PBW field infestations averaged over 2.5 live larvae per non-Bt cotton immature green boll compared with no live larvae in Bt immature green bolls. In bioassays, using laboratory-reared cabbage looper (CL), larval mortality percentages decreased with decreasing toxic protein content measured in Bt leaves. The toxic protein was expressed in cotton bolls and leaves from overwintered Bt plants. PBW and tobacco budworm (TBW) larval mortalities averaged 99 and 100% (overwintered and 2002 seeded Bt cotton), respectively, compared with averages of 40 and 3%, respectively, on non-Bt bolls and leaves (overwintered and 2002 seeded cotton).

Technical Abstract: NuCOTN 33B® (Bt) and Delta and Pineland (DPL 5415) cottons were grown in furrow and furrow plus drip irrigated cotton plots in Arizona. Cry1Ac toxic protein produced in Bt cotton was measured with commercially available enzyme-linked immunosorbent assay (ELISA) kits. Irrigation type had no effect on Cry1Ac measured in cotton leaves or bolls. First-instar, laboratory-reared pink bollworm (PBW), Pectinophora gossypiella (Saunders), larvae placed on Bt cotton bolls collected in field throughout the season died (100%) irrespective of decreasing Cry1Ac toxic protein levels in late season bolls. PBW field infestations averaged over 2.5 live larvae per (DPL 5415) immature green boll compared with no live larvae in Bt immature green bolls. Results were similar for PBW infestations of open mature bolls on Bt and DPL 5415 whole cotton plant samples. Two unexplained PBW larval exit holes occurred in open mature Bt bolls. These could have been on plants from non-Bt contaminated seed in Bt seed lots. In bioassays, using laboratory-reared cabbage looper (CL), Trichoplusia ni (Hübner), larval mortality percentages decreased with decreasing Cry1Ac content measured in Bt leaves. Cry1Ac protein was expressed in cotton bolls and leaves from overwintered Bt plants. PBW and tobacco budworm (TBW), Heliothis virescens (L.), larval mortalities averaged 99 and 100% (overwintered and 2002 seeded Bt cotton), respectively, compared with averages of 40 and 3%, respectively, on DPL 5415 bolls and leaves (overwintered and 2002 seeded cotton).

Last Modified: 8/19/2014
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