Abstract
Spodoptera frugiperda (J. E. Smith) is one of the major pests of maize in Argentina. The main tool for its control is the use of genetically modified maize hybrids expressing Bacillus thuringiensis (Bt) insecticidal proteins. Maize growers in Argentina initially controlled this pest with Bt maize that expressed a single Bt protein (Cry1Ab or Cry1F). Currently it is necessary to plant maize cultivars that produce two Bt proteins to achieve the satisfactory control. Recently, Cry1F field-evolved resistant populations of this species were confirmed in Argentina. The objective of this study was to evaluate the performance of S. frugiperda field-collected strains on different Bt and non-Bt maize hybrids. Strains were collected from non-Bt maize (T1), Agrisure TDMax (T2), Agrisure Viptera (T3), Agrisure Viptera 3110 (T4), Genuity VT Triple Pro (T5), and Power Core (T6). Three experiments were performed to 1) determine the survivorship and reproduction of field-collected larvae (F0) from Bt maize hybrids, 2) evaluate Cry1F resistance using an F1 screen, and 3) assess the performance of F1 strains on different maize hybrids. In the F0, the survivorship from larva to adult ranged from 0 to 63%. We obtained adults from only the T1, T2, T5, and T6 strains with no significant differences in the reproductive parameters. Continuously rearing F1 larvae on their collected hosts affected larval duration, which was significantly shorter for a known-laboratory Bt-susceptible strain than the field-collected strains. Our results support the existence of Cry1F-resistance alleles in S. frugiperda field populations in Argentina.
Highlights
Yang et al (2016) evaluated larvae of SS, RR, and RS genotypes of fall armyworm on pyramided and single-gene Bacillus thuringiensis (Bt) cotton. They found that all genotypes were susceptible to the pyramided cotton and the single-gene cotton containing Cry2Ae, whereas the pyramided cotton containing Cry1Ac/Cry1F was effective against SS and RS, but not for RR. These results showed that the Cry1F-maize–selected fall armyworm can cause cross-crop resistance to other Bt crops expressing similar insecticidal proteins
The objectives of this study were to 1) determine the performance of fall armyworm collected from various Bt maize hybrids in the field after continuous rearing on the same collected hybrid and 2) evaluate the performance of fall armyworm resistance to Cry1F when continuously reared on non-Bt and Bt maize hybrids grown in the field
By evaluating the biological parameters of fall armyworm strains over multiple generations, we found developmental delays in the field-collected populations, relatively to a known Bt-susceptible laboratory strain, which could affect the success of Bt maize insect resistant management (IRM) in fall armyworm
Summary
The objective of this study was to evaluate the performance of S. frugiperda field-collected strains on different Bt and non-Bt maize hybrids. Three experiments were performed to 1) determine the survivorship and reproduction of field-collected larvae (F0) from Bt maize hybrids, 2) evaluate Cry1F resistance using an F1 screen, and 3) assess the performance of F1 strains on different maize hybrids. The most widely used tool for fall armyworm control in Argentina is the use of the genetically modified maize hybrids expressing Bacillus thuringiensis (Bt) insecticidal proteins (Blanco et al 2010, Huang et al 2014). Monitoring studies of Bt hybrids expressing Cry1F performed in the most important maize growth regions in Argentina from 2009 to 2015 confirmed resistance of fall armyworm field populations to the Cry1F maize (Chandrasena et al 2017). Comparing the performance of susceptible and resistant insects on Bt maize hybrids can help understand fitness costs and improve IRM (Wu et al 2002)
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