Inheritance of resistance to Bt canola in a field-derived population of Plutella xylostella

• Published in: Pest management science 2003-11, Vol.59 (11), p.1197-1202
• Main Authors: Sayyed, A.H, Schuler, T.H, Wright, D.J
• Format: Article
• Language: English
• Subjects: Animals; Bacillus thuringiensis; Bacterial Proteins - analysis; Bacterial Proteins - biosynthesis; Bacterial Proteins - genetics; Bacterial Toxins - biosynthesis; Bacterial Toxins - genetics; Biological and medical sciences; Biological Assay; biological control; Brassica napus - chemistry; Brassica napus - genetics; Brassica napus - parasitology; Brassica napus var. napus; Bt transgenic plants; canola; Endotoxins - analysis; Endotoxins - biosynthesis; Endotoxins - genetics; Female; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes, Insect; Genes, Recessive - genetics; Hemolysin Proteins; Heterozygote; incomplete dominance; inheritance (genetics); insect control; insect pests; insecticidal proteins; insecticide resistance; Insecticide Resistance - genetics; Larva - genetics; Larva - growth & development; Male; maternal influence; Moths - genetics; Moths - growth & development; Multifactorial Inheritance; Pest Control, Biological; Phytopathology. Animal pests. Plant and forest protection; Plant Leaves - chemistry; plant pests; Plants, Genetically Modified - genetics; Plants, Genetically Modified - parasitology; Plutella xylostella; transgenic plants
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.754

Crops expressing Bacillus thuringiensis (Bt) insecticidal Cry proteins are grown on millions of hectares. Recommendations to delay resistance are based on a high expression/refugia strategy that aims to kill resistant heterozygotes and enable some susceptible insects to survive. Leaf-dip bioassays on F1 crosses of Malaysian populations of diamondback moth (Plutella xylostella (L)) showed that Cry1Ac resistance was not fully recessive. The survival of ca 50% of heterozygotes on Bt canola (Brassica napus L) leaves expressing low concentrations of Cry1Ac agreed with a non-fully-recessive model for resistance. Extrapolations based on log dose-logit mortality regressions for heterozygotes using leaf-dip bioassays showed that a relatively high level of expression, of ca 2000 ng Cry1Ac mg-1 total leaf protein, would be required to give 90% mortality to heterozygotes. If high enough levels of expression of Bt toxin to kill heterozygotes cannot be achieved and maintained under field conditions, the effectiveness of the high-dose/refugia strategy would be reduced.