title: Differential toxicity of Bacillus thuringiensis strains and their crystal toxins against high-altitude Himalayan populations of diamondback moth, Plutella xylostella L.
abstract: BACKGROUND
  Diamondback moth, Plutella xylostella (L.), is a major insect pest of crucifers in the biodiversity-rich north-western Indian Himalayan hills. The present investigation was aimed at determining the susceptibility pattern of P. xylostella populations collected from different locations of this region to autochthonous and standard Bacillus thuringiensis strains.
  
  
  RESULTS
  Among the reference as well as indigenous B. thuringiensis strains tested, sub spp. kurstaki HD-1, kurstaki HD-73, galleriae HD-8, local galleriae/colmeri strain BtOa1 and some of their Cry1 class toxins were found to be highly toxic. Surprisingly, the sub sp. tolworthi HD-125, local tolworthi strain BtHa1 and Cry9 class toxins were found to be non-toxic. Midgut homogenate from fourth-instar larvae was found to activate 130 kDa protoxin from the local tolworthi strain BtHa1 into 68 kDa toxin, but failed to exert any larval mortality, probably owing to lack of receptor binding.
  
  
  CONCLUSIONS
  The present study provides valuable baseline susceptibility data for the deployment of B. thuringiensis-based control methods, as well as for future monitoring of development of resistance in P. xylostella to B. thuringiensis in this ecologically sensitive region.
authors.affiliation: Vivekananda Institute of Hill Agriculture (ICAR), Almora, Uttarakhand, India. mohan_iari@yahoo.com
authors.forename: Muthugounder
authors.initials: M
authors.lastname: Mohan
authors.forename: Satya N
authors.initials: SN
authors.lastname: Sushil
authors.forename: Govindan
authors.initials: G
authors.lastname: Selvakumar
authors.forename: Jagadish C
authors.initials: JC
authors.lastname: Bhatt
authors.forename: Govind T
authors.initials: GT
authors.lastname: Gujar
authors.forename: Hari S
authors.initials: HS
authors.lastname: Gupta
mesh_terms: D000531:Altitude; D000818:Animals; D001413:Bacillus thuringiensis / Q000145:classification* / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism* / Q000494:pharmacology*; D001681:Biological Assay; D003710:Demography; D009036:Moths / Q000187:drug effects* / Q000502:physiology*; D012988:Soil Microbiology
chemical_list: D001427:Bacterial Toxins