title: Pest control and resistance management through release of insects carrying a male-selecting transgene.
abstract: BACKGROUND
  Development and evaluation of new insect pest management tools is critical for overcoming over-reliance upon, and growing resistance to, synthetic, biological and plant-expressed insecticides. For transgenic crops expressing insecticidal proteins from the bacterium Bacillus thuringiensis ('Bt crops') emergence of resistance is slowed by maintaining a proportion of the crop as non-Bt varieties, which produce pest insects unselected for resistance. While this strategy has been largely successful, multiple cases of Bt resistance have now been reported. One new approach to pest management is the use of genetically engineered insects to suppress populations of their own species. Models suggest that released insects carrying male-selecting (MS) transgenes would be effective agents of direct, species-specific pest management by preventing survival of female progeny, and simultaneously provide an alternative insecticide resistance management strategy by introgression of susceptibility alleles into target populations. We developed a MS strain of the diamondback moth, Plutella xylostella, a serious global pest of crucifers. MS-strain larvae are reared as normal with dietary tetracycline, but, when reared without tetracycline or on host plants, only males will survive to adulthood. We used this strain in glasshouse-cages to study the effect of MS male P. xylostella releases on target pest population size and spread of Bt resistance in these populations.
  
  
  RESULTS
  Introductions of MS-engineered P. xylostella males into wild-type populations led to rapid pest population decline, and then elimination. In separate experiments on broccoli plants, relatively low-level releases of MS males in combination with broccoli expressing Cry1Ac (Bt broccoli) suppressed population growth and delayed the spread of Bt resistance. Higher rates of MS male releases in the absence of Bt broccoli were also able to suppress P. xylostella populations, whereas either low-level MS male releases or Bt broccoli alone did not.
  
  
  CONCLUSIONS
  These results support theoretical modeling, indicating that MS-engineered insects can provide a powerful pest population suppressing effect, and could effectively augment current Bt resistance management strategies. We conclude that, subject to field confirmation, MS insects offer an effective and versatile control option against P. xylostella and potentially other pests, and may reduce reliance on and protect insecticide-based approaches, including Bt crops.
authors.affiliation: Department of Zoology, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3PS, UK.|Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Harvey-Samuel
authors.affiliation: Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK. neil.morrison@oxitec.com.
authors.forename: Neil I
authors.initials: NI
authors.lastname: Morrison
authors.affiliation: Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Walker
authors.affiliation: Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.
authors.forename: Thea
authors.initials: T
authors.lastname: Marubbi
authors.affiliation: Cornell University/NYSAES, Barton Lab 416, 630 W. North Street, Geneva, NY, 14456, USA.|Institute of Plant Protection, Xinjiang Academy of Agricultural Science, Urumqi, China.
authors.forename: Ju
authors.initials: J
authors.lastname: Yao
authors.affiliation: Cornell University/NYSAES, Barton Lab 416, 630 W. North Street, Geneva, NY, 14456, USA.
authors.forename: Hilda L
authors.initials: HL
authors.lastname: Collins
authors.affiliation: Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.
authors.forename: Kevin
authors.initials: K
authors.lastname: Gorman
authors.affiliation: Biological Chemistry & Crop Protection Department, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: T G Emyr
authors.initials: TG
authors.lastname: Davies
authors.affiliation: Department of Zoology, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3PS, UK.|Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK.
authors.forename: Nina
authors.initials: N
authors.lastname: Alphey
authors.affiliation: Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Warner
authors.affiliation: Cornell University/NYSAES, Barton Lab 416, 630 W. North Street, Geneva, NY, 14456, USA.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Shelton
authors.affiliation: Department of Zoology, University of Oxford, South Parks Road, Oxford, Oxfordshire, OX1 3PS, UK.|Oxitec Ltd, 71 Innovation Drive, Milton Park, Oxford, Oxfordshire, OX14 4RQ, UK.|The Pirbright Institute, Woking, Surrey, GU24 0NF, UK.
authors.forename: Luke
authors.initials: L
authors.lastname: Alphey
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics*; D001413:Bacillus thuringiensis / Q000235:genetics; D001937:Brassica / Q000235:genetics / Q000469:parasitology*; D018556:Crops, Agricultural / Q000235:genetics / Q000469:parasitology*; D005260:Female; D005818:Genetic Engineering; D007305:Insecticide Resistance; D008297:Male; D009036:Moths / Q000235:genetics* / Q000502:physiology; D010572:Pest Control, Biological / Q000379:methods*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000469:parasitology; D019076:Transgenes