Diverse genetic basis of field-evolved resistance to Bt cotton in cotton bollworm from China

Abstract

Evolution of pest resistance reduces the efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays or in transgenic crops. Although several pests have evolved resistance to Bt crops in the field, information about the genetic basis of field-evolved resistance to Bt crops has been limited. In particular, laboratory-selected resistance to Bt toxin Cry1Ac based on recessive mutations in a gene encoding a toxin-binding cadherin protein has been identified in three major cotton pests, but previous work has not determined if such mutations are associated with field-selected resistance to Bt cotton. Here we show that the most common resistance alleles in field populations of cotton bollworm, Helicoverpa armigera , selected with Bt cotton in northern China, had recessive cadherin mutations, including the deletion mutation identified via laboratory selection. However, unlike all previously studied cadherin resistance alleles, one field-selected cadherin resistance allele conferred nonrecessive resistance. We also detected nonrecessive resistance that was not genetically linked with the cadherin locus. In field-selected populations, recessive cadherin alleles accounted for 75–84% of resistance alleles detected. However, most resistance alleles occurred in heterozygotes and 59–94% of resistant individuals carried at least one nonrecessive resistance allele. The results suggest that resistance management strategies must account for diverse resistance alleles in field-selected populations, including nonrecessive alleles.

Genetic hitchhiking and resistance evolution to transgenic Bt toxins: insights from the African stalk borer Busseola fusca (Noctuidae)

“…Indeed, increased survival on Bt maize obtained in a F2 sib-cross clearly suggested the existence of at least one recessive resistance trait in A 2 . Similarly to what has already been reported in another pest (e.g., Zhang et al, 2012;Jin et al, 2013), diverse resistance mutations characterised by different levels of recessiveness might therefore be responsible for the observed pattern of widespread field resistance to Bt maize in South Africa.…”

“…Multiple recessive mutations that cause resistance to Cry1A toxins in Lepidoptera have been reported (see Heckel et al, 2007) in genes encoding Cadherin-like proteins (e.g., Morin et al, 2003) and ABC transporters (e.g., Baxter et al, 2011). In the field, diverse alleles conferring resistance were identified within Chinese populations of Helicoverpa armigera (Zhang et al, 2012), including recessive resistance alleles at the Cadherin locus as well as two non-recessive mutations, one of which was not linked to this locus.…”

Social Impacts of GM Crops in Agriculture: A Systematic Literature Review

“…It is also likely that farmers do not receive the information and advice needed to cultivate the crop correctly. Resistance development in pest insects has been confirmed for both Bt maize and Bt cotton [127,128] and may partly be the result of inappropriate management regimes. This leads us to support previous claims for the importance of resolving the conflict between sufficient regulation of GM crop use and making GM crops accessible to marginalised farmers [31].…”

Resistance to Bt Crops; Influence, mechanisms and management strategies

“…This case was reported after 7 years after being introduced by Bt cotton (Jensen, 2008). Then, different cases of resistance to Bt toxins has been stated in different Bt crops, such as, pink bollworm Pectinophora gossypiella evolved resistance to Cry1Ac in Bt cotton (Dennehy et al, 2004;Tabashnik et al, 2002Tabashnik et al, , 2000Zhang et al, 2012), Spodoptera frugiperda to Cry1F in Bt corn, Busseola fusca (Fuller) to Cry1Ab in Bt corn, Helicoverpa punctigera and Helicoverpa armigera to Cry2Ab in Bt cotton (Downes et al, 2010;Kruger et al, 2011;Mahon et al, 2007;SantosAmaya et al, 2016;Van Rensburg, 2007). Diabrotica virgifera virgifera showed resistance to Cry3Bb1 in Bt maize (Gassmann et al, 2011).…”