title: Field resistance to the Bacillus thuringiensis protein Cry1Ac expressed in Bollgard(®) hybrid cotton in pink bollworm, Pectinophora gossypiella (Saunders), populations in India.
abstract: BACKGROUND
  Bollgard(®) cotton, expressing Cry1Ac insecticidal protein, was approved for commercial planting in India in 2002, and by 2009 constituted 87% of the Indian crop, reducing losses from lepidopteran pests, including pink bollworm (PBW), Pectinophora gossypiella. Inadequate control of PBW in fields of single-gene Bollgard cotton was reported in 2009; surveys revealed heavy infestations of PBW in Bollgard, restricted to Gujarat state, but not elsewhere in India.
  
  
  RESULTS
  Bioassays of PBW strains from Bollgard bolls showed that, while susceptible PBW could not complete development to third and later instar at 10.0 µg Cry1Ac mL(-1) , 66.1% of larvae from Gujarat Bollgard strains could. A field-resistant strain, further selected in the laboratory, had susceptibility to Cry1Ac reduced by >2000-fold. Resistance to Cry1Ac did not confer cross-resistance to the Cry2Ab2 protein. In 2010, Bollgard fields in Gujarat continued to be infested with PBW, and many Bollgard fields in the adjoining states of Maharashtra and Madhya Pradesh showed high-level infestation by PBW.
  
  
  CONCLUSIONS
  Inadequate planting of refuges for PBW is the likely explanation for the field resistance to Bt cotton observed in Gujarat. These findings underscore the higher vulnerability of single-gene Bt products relative to dual-gene products expressing Cry1Ac and Cry2Ab2, and the increased risk of resistance evolution with low refuge compliance.
authors.affiliation: Monsanto Research Centre, Bangalore, Karnataka, India.
authors.forename: Komarlingam S
authors.initials: KS
authors.lastname: Mohan
authors.affiliation: Monsanto Research Centre, Bangalore, Karnataka, India.
authors.forename: Kadanur C
authors.initials: KC
authors.lastname: Ravi
authors.affiliation: Mahyco Monsanto Biotech (India) Ltd, Mumbai, Maharashtra, India.
authors.forename: Pennadam J
authors.initials: PJ
authors.lastname: Suresh
authors.affiliation: Monsanto Company, St Louis, MO, USA.
authors.forename: Douglas
authors.initials: D
authors.lastname: Sumerford
authors.affiliation: Monsanto Company, St Louis, MO, USA.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Head
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D001681:Biological Assay; D004731:Endotoxins / Q000235:genetics*; D015870:Gene Expression; D003368:Gossypium / Q000235:genetics*; D006460:Hemolysin Proteins / Q000235:genetics*; D007194:India; D007814:Larva; D007915:Lepidoptera / Q000502:physiology; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bollgard; Cry1Ac; Cry2Ab2; Pectinophora gossypiella; insect resistance; transgenic cotton