Response of larval Chironomus tepperi (Diptera: Chironomidae) to individual Bacillus thuringiensis var. israelensis toxins and toxin mixtures.
The biopesticide Bacillus thuringiensis israelensis (B.t.i.) is highly toxic to the larvae of Chironomus tepperi, an important pest of aerially sown rice in southern Australia. In this study, all of the known Cry genes and the Cyt1A gene from B.t.i. were expressed and tested for individual toxicity against fourth instar C. tepperi larvae. Possible synergism between toxins in two component mixtures involving all toxins except Cry10A was also evaluated. Of the Cry toxins, only Cry11A and Cry4B displayed substantial toxicity; however, both were 10- to 20-fold less toxic than the parental B.t.i. strain. The only detected synergy was between the mildly toxic Cry4A and Cyt1A toxins. In direct contrast to previous studies with mosquitoes, mixtures of Cry11A/Cry4B and Cry11A/Cyt1A were mildly antagonistic. The activity of Cry11A and Cry4B is sufficient to justify investigation as to whether their expression in transgenic rice plants could provide control of C. tepperi larvae.
Hughes
Peter A
PA
CSIRO Division of Plant Industry, GPO Box 1600, Canberra ACT 2601, Australia. Peter.Hughes@csiro.au
Stevens
Mark M
MM
Park
Hyun-Woo
HW
Federici
Brian A
BA
Dennis
Elizabeth S
ES
Akhurst
Ray
R
D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology; D001426:Bacterial Proteins / Q000633:toxicity*; D001427:Bacterial Toxins / Q000633:toxicity*; D002683:Chironomidae / Q000187:drug effects*; D004731:Endotoxins / Q000633:toxicity*; D007814:Larva / Q000187:drug effects; D012275:Oryza / Q000382:microbiology; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified / Q000382:microbiology
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins