Genes and environment interact to determine the fitness costs of resistance to Bacillus thuringiensis.
Genes which provide resistance to novel challenges such as pesticides, toxins or pathogens often impose fitness costs on individuals with a resistant phenotype. Studies of resistance to Bacillus thuringiensis and its insecticidal Cry toxins indicate that fitness costs may be variable and cryptic. Using two field populations (Karak and Serd4) of the diamondback moth, Plutella xylostella, we tested the hypothesis that the costs associated with resistance to the B. thuringiensis toxin Cry1Ac would be evident when insects were grown under poor environmental conditions, namely limited or poor quality resources. On a poor quality resource, a cultivar of Brassica oleracea var. capitata with varietal resistance to P. xylostella, only one resistant population, Karak, showed reduced fitness. Conversely, when we limited a high quality resource, Brassica pekinensis, by imposing larval competition, only resistant Serd4 insects had reduced survival at high larval densities. Furthermore, Cry1Ac resistance in Serd4 insects declined when reared at high larval densities while resistance at low densities fluctuated but did not decline significantly. These results confirm the hypothesis that resistance costs can appear under stressful conditions and demonstrate that the fitness cost of resistance to Bacillus thuringiensis can depend on the particular interaction between genes and the environment.
Raymond
Ben
B
Department of Biological Sciences, Imperial College London, Silwood Park campus, Ascot, Berks SL5 7PY, UK. benjamin.raymond@zoo.ox.ac.uk
Sayyed
Ali H
AH
Wright
Denis J
DJ
D000704:Analysis of Variance; D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D001427:Bacterial Toxins / Q000633:toxicity*; D001937:Brassica; D004731:Endotoxins / Q000633:toxicity*; D004777:Environment; D006460:Hemolysin Proteins; D007305:Insecticide Resistance / Q000235:genetics; D007814:Larva / Q000254:growth & development; D016014:Linear Models; D009036:Moths / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D011156:Population Density; D016019:Survival Analysis
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis