Insect resistant Bt crops are widely grown in many countries all over the
world to prevent pest attacks in highly economical crops. However, the
ability of pests to rapidly evolve resistance reduces the efficacy of Bt
crops. In an article published by Scientific Reports, scientists from Hubei
Academy of Agricultural Sciences and Chinese Academy of Agricultural
Sciences reported that transposon insertion causes cadherin mis-splicing and
confers resistance to Bt cotton in pink bollworm, a devastating pest of
cotton globally.

The researchers found the allele (r15) harboring the insertion in a field
population from China. They described the insertion as a miniature inverted
repeat transposable element (MITE) with two additional transposons and
produces two mis-spliced transcript variants. A strain homozygous for r15
had 290-fold resistance to Cry1Ac, little or no cross-resistance to Cry2Ab,
and completed its life cycle on Bt cotton producing Cry1Ac. The researchers
also reported that for transformed insect cells, susceptibility to Cry1Ac
was higher for cells producing the wild-type cadherin than for cells
producing the r15 mutant proteins.

The similar resistance of pink bollworm to Cry1Ac in laboratory- and
field-selected insects from China, India and the US provides a basis for
developing international resistance management practices.

[www.nature.com]