J. Gonzalez-cabrera et al., High genetic variability for resistance to Bacillus thuringiensis toxins in a single population of diamondback moth, APPL ENVIR, 67(11), 2001, pp. 5043-5048
The long-term benefit of insecticidal products based on Cry toxins, either
in sprays or as transgenic crops, is threatened by the development of resis
tance by target pests. The models used to predict evolution of resistance t
o Cry toxins most often are monogenic models in which two alleles are used.
Moreover, the high-dose/refuge strategy recommended for implementation wit
h transgenic crops relies on the assumption that the resistance allele is r
ecessive. Using selection experiments, we demonstrated the occurrence in a
laboratory colony of diamondback moth of two different genes (either alleli
c or nonallelic) that confer resistance to Cry1Ab. At the concentration tes
ted, resistance was dominant in one selection line and partially recessive
in the other. Resistant insects from the two selection lines also differed
in their cross-resistance patterns. The diamondback moth colony was derived
from a field population from the Philippines, which originally showed a di
fferent resistance phenotype. This is the first time that an insect populat
ion has been directly shown to carry more than one gene conferring resistan
ce to the same Cry toxin.