Varied frequencies of resistance alleles to Cry1Ab and Cry1Ac among Brazilian populations of the sugarcane borer, Diatraea saccharalis (F.)

Abstract

BACKGROUND: Brazil is the largest grower of the world's 26 million ha of sugarcane, Saccharum officinarum. Pest damage mainly by the sugarcane borer, Diatraea saccharalis (F.), is a great challenge to the sugarcane industry. To control D. saccharalis, Brazil launched the world's first commercial use of Bt sugarcane in 2017. As part of the resistance management programs for Bt sugarcane planting, 535 F 2 isoline families of D. saccharalis collected from three major sugarcane planting states (Goiás, Minas Gerais and São Paulo) in Brazil during 2019-2020 were screened for resistance to two Bt sugarcane varieties: CTC20BT expressing Cry1Ab and CTC9001BT expressing Cry1Ac. Here we report the results of the first study related to Bt resistance in a sugarcane cropping system. RESULTS: Larval survivorships of these families in an F 2 screen on CTC20BT were highly correlated with their survival on CTC9001BT, whereas the Cry1Ac tissues exhibited greater insecticidal activities than Cry1Ab. Resistance allele frequencies (RAFs) for populations from Goiás and Minas Gerais were relatively low at 0.0034 for Cry1Ab and 0.0045 to Cry1Ac. By contrast, RAFs for São Paulo populations were considerably greater (0.0393 to Cry1Ab, 0.0245 to Cry1Ac).CONCLUSIONS: RAFs to Cry1Ab and Cry1Ac varied among Brazilian D. saccharalis populations. Prior selection resulting from an intensive use of single-gene Bt maize under low compliance of refuge planting could be a main factor contributing to the high RAF in São Paulo. The results suggest that mitigation measures including sufficient non-Bt maize refuge planting, effective resistance monitoring, and use of pyramided Bt sugarcane traits should be implemented promptly to prevent further increase in the RAF to ensure the sustainable use of Bt sugarcane in Brazil.

Global Patterns of Insect Resistance to Transgenic Bt Crops: The First 25 Years

“…F 2 screens conducted during the 2019-2020 season revealed significantly higher resistance allele frequency in São Paulo (0.0393 for Cry1Ab and 0.0245 for Cry1Ac) than in the neighboring states of Goiás and Minas Gerais (0.0034 for Cry1Ab and 0.0045 for Cry1Ac). Given that Bt sugarcane accounted for less than 0.1% of Brazil's sugarcane in 2019–2020, Oliveira et al (2022) conclude the resistance reflects previous selection from single-toxin Bt maize grown extensively in São Paulo with limited refuges.…”

“…The mean time from commercial introduction to detection of resistance in these 17 cases is 8.6 yr (SE = 1.3, Table 3). Two notable cases involve D. saccharalis resistance to Cry1Ab and Cry1Ac produced by Bt sugarcane in Brazil (Oliveira et al 2022). F 2 screens conducted during the 2019-2020 season revealed significantly higher resistance allele frequency in São Paulo (0.0393 for Cry1Ab and 0.0245 for Cry1Ac) than in the neighboring states of Goiás and Minas Gerais (0.0034 for Cry1Ab and 0.0045 for Cry1Ac).…”

Fitness Costs and Incomplete Resistance Associated with Delayed Evolution of Practical Resistance to Bt Crops

“…Transgenic crops that produce toxins from the soil bacterium Bacillus thuringiensis (Bt) can reduce insect feeding damage on crops including corn, cotton, cowpea, eggplant, soybean, and sugarcane planted on large and small farms [ 1 , 2 , 3 , 4 , 5 ]. Advantages of Bt crops include a lower reliance on insecticide sprays for pest control [ 6 , 7 , 8 , 9 ], reduction in pest pressure across agricultural landscapes [ 8 , 10 , 11 , 12 ], and pest eradication [ 13 ].…”

Correction to: Global Patterns of Insect Resistance to Transgenic Bt Crops: The First 25 Years

“…F 2 screens conducted during the 2019-2020 season revealed significantly higher resistance allele frequency in São Paulo (0.0393 for Cry1Ab and 0.0245 for Cry1Ac) than in the neighboring states of Goiás and Minas Gerais (0.0034 for Cry1Ab and 0.0045 for Cry1Ac). Given that Bt sugarcane accounted for less than 0.1% of Brazil's sugarcane in 2019-2020, Oliveira et al (2022) conclude the resistance reflects previous selection from single-toxin Bt maize grown extensively in São Paulo with limited refuges.…”