Broad-spectrum cross-resistance in Spodoptera exigua from selection with a marginally toxic Cry protein.
BACKGROUND
Spodoptera exigua (Hübner) has developed resistance to a wide range of chemical insecticides. Products based on Bacillus thuringiensis Cry toxins are used in integrated pest management as an ecologically friendly alternative for pest control. Since there are few B. thuringiensis Cry proteins highly active against S. exigua, it is desirable to apply appropriate resistance management strategies to prevent the evolution of resistance to these proteins.


RESULTS
Spodoptera exigua larvae were selected with Cry1Ab, a protein with low activity against this pest. Selected larvae developed > 30-fold resistance to Cry1Ab in 13 generations, relative to an unselected strain. The estimated realised heritability (h(2)) for the first five generations of selection was 0.15. Cross-resistance was also observed to the more active proteins Cry1Ca, Cry1Da and Cry1Fa (>20, 26 and > 8 respectively). The activity of midgut proteases to degrade the ingested toxin was tested, although no differences in activity were found between selected and unselected larvae.


CONCLUSIONS
Spodoptera exigua is able to evolve cross-resistance to highly active Cry proteins when exposed to a protein with marginal toxicity to this species. It is important to take this into account in areas where S. exigua is a secondary pest and B. thuringiensis Cry1A toxins are used to control other pests.
Hernández-Martínez
Patricia
P
Departament de Genètica, Universitat de València, Valencia, Spain.
Ferré
Juan
J
Escriche
Baltasar
B
D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000633:toxicity*; D004731:Endotoxins / Q000737:chemistry / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000633:toxicity*; D007305:Insecticide Resistance; D007306:Insecticides / Q000737:chemistry / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018411:Spodoptera / Q000187:drug effects* / Q000235:genetics / Q000502:physiology
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis