scholarly journals Susceptibility of Fall Armyworms (Spodoptera frugiperda J.E.) from Mexico and Puerto Rico to Bt Proteins

Insects ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 831
Author(s):  
Rebeca Gutierrez-Moreno ◽  
David Mota-Sanchez ◽  
Carlos A. Blanco ◽  
Desmi Chandrasena ◽  
Christina Difonzo ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Spodoptera Frugiperda ◽  
Fall Armyworm ◽  
Effective Concentration ◽  
Bt Corn ◽  
Median Lethal Concentration ◽  
The Status ◽  
Different Populations ◽  
Loss Of Susceptibility ◽  
Mexican Populations

Fall armyworm is one of the main pests of conventional and Bacillus thuringiensis (Bt) corn in many countries in the Americas, Africa, Asia and in Australia. We conducted diet-overlay bioassays to determine the status of susceptibility to four Bt proteins (Cry1A.105, Cry2Ab2, Cry1F and Cry1Ac) in three different populations of fall armyworm from Mexico, and one population from Puerto Rico. Bioassays showed that fall armyworms from Puerto Rico were resistant to Cry1F with a resistance ratio 50 (RR50) higher than 10,000 ng/cm2 and to Cry1Ac with a RR50 = 12.2 ng/cm2, displaying the highest median lethal concentration (LC50) values to all Bt proteins tested. The effective concentration 50 (EC50) values further confirmed the loss of susceptibility to Cry1F and Cry1Ac in this population. However, LC50 and EC50 results with Cry1A.105 and Cry2Ab2 revealed that fall armyworm from Puerto Rico remained largely susceptible to these two proteins. The Mexican populations were highly susceptible to all the Bt proteins tested and displayed the lowest LC50 and EC50 values to all Bt proteins. Our results suggest that Cry1F and Cry1Ac resistance is stable in fall armyworm from Puerto Rico. However, this population remains susceptible to Cry1A.105 and Cry2Ab2. Results with Mexican fall armyworms suggest that possible deployment of Bt corn in Mexico will not be immediately challenged by Bt-resistant genes in those regions.

Virulence and Genetic Characterization of Six Baculovirus Strains Isolated From Different Populations of Spodoptera Frugiperda (Lepidoptera: Noctuidae)

2021 ◽  
Author(s):  
Ingrid Zanella-Saenz ◽  
Elisabeth A. Herniou ◽  
Jorge E. Ibarra ◽  
Ma.Cristina Del Rincón-Castro ◽  
Ilse Alejandra Huerta-Arredondo
Keyword(s):  
Biological Control ◽  
Cell Cultures ◽  
Spodoptera Frugiperda ◽  
Fall Armyworm ◽  
The United States ◽  
Infection Mechanisms ◽  
Different Populations

Abstract Fall armyworm (FAW), Spodoptera frugiperda (Smith, 1797), is a polyphagous, voracious, and economically important agricultural pest. Biological control of FAW is a strategy that must be further explored. This study evaluated six baculovirus strains isolated from infected FAW larvae from Mexico, Argentina, Honduras, and the United States. Five alphabaculoviruses (SfNPV-An2, SfNPV-Arg, SfNPV-Fx, SfNPV-Ho and SfNPV-Sin) and one betabaculovirus (SfGV-RV), were tested against FAW larvae, showing a wide diversity of virulence levels among strains when their estimated LC50s were compared, being SfNPVArg, SfNPV-Ho and SfNPV-Fx more virulent than SfNPV-An 2 , SfNPV-Sin and SfGV-RV. To determine any virulence difference in vitro studies of these isolates, Sf9 cell cultures were used. Interestingly, only ODVs from four of the test SfNPV strains showed infectivity on Sf9 cell cultures, and some differences in virulence were observed. Genomic restriction analyses and partial sequences of lef-8, lef-9 , and polh/granulin genes showed little variability among alphabaculoviruses, both, among them and with previously reported sequences. However, sequences from SfGV-RV were closer to previously reported sequences from the SfGVVG008 strain than the SfGV-Arg and SfGV-VG014 strains. The great difference in the in vivo virulence was not correlated with great similarity among the isolates. The characterization of these six baculoviruses isolates offers the basis for exploring their potential as biological control agents against S. frugiperda, as well the initial studies on their specific infection mechanisms, evolution, and ecology.

scholarly journals Whole genome comparisons reveal panmixia among fall armyworm (Spodoptera frugiperda) from diverse locations

2020 ◽  
Author(s):  
Katrina A. Schlum ◽  
Kurt Lamour ◽  
Caroline Placidi de Bortoli ◽  
Rahul Banerjee ◽  
Scott J. Emrich ◽  
...  
Keyword(s):  
United States ◽  
Puerto Rico ◽  
Gene Flow ◽  
Spodoptera Frugiperda ◽  
Fall Armyworm ◽  
The United States ◽  
Genomic Diversity ◽  
Whole Genome ◽  
Long Distance ◽  
Host Strains

AbstractThe fall armyworm (Spodoptera frugiperda (J.E. Smith)) is a highly polyphagous agricultural pest with long-distance migratory behavior threatening food security worldwide. This pest has a host range of >80 plant species, but two host strains are recognized based on their association with corn (C-strain) or rice and smaller grasses (R-strain). In this study, the population structure and genetic diversity in 55 S. frugiperda samples from Argentina, Brazil, Kenya, Puerto Rico and the United States (USA) were surveyed to further our understanding of whole genome nuclear diversity. Comparisons at the genomic level suggest panmixia in this population, other than a minor reduction in gene flow between the two overwintering populations in the continental USA that also corresponded to genetically distinct host strains. Two maternal lines were detected from analysis of mitochondrial genomes. We found members from the Eastern Hemisphere interspersed within both continental USA overwintering subpopulations, suggesting multiple individuals were likely introduced to Africa. Comparisons between laboratory-reared and field collected S. frugiperda support similar genomic diversity, validating the experimental use of laboratory strains. Our research is the largest diverse collection of United States S. frugiperda whole genome sequences characterized to date, covering eight continental states and a USA territory (Puerto Rico). The genomic resources presented provide foundational information to understand gene flow at the whole genome level among S. frugiperda populations.

scholarly journals Whole genome comparisons reveal panmixia among fall armyworm (Spodoptera frugiperda) from diverse locations

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Katrina A. Schlum ◽  
Kurt Lamour ◽  
Caroline Placidi de Bortoli ◽  
Rahul Banerjee ◽  
Robert Meagher ◽  
...  
Keyword(s):  
United States ◽  
Puerto Rico ◽  
Gene Flow ◽  
Spodoptera Frugiperda ◽  
Fall Armyworm ◽  
The United States ◽  
Whole Genome ◽  
Long Distance ◽  
Field Samples ◽  
Host Strains

Abstract Background The fall armyworm (Spodoptera frugiperda (J.E. Smith)) is a highly polyphagous agricultural pest with long-distance migratory behavior threatening food security worldwide. This pest has a host range of > 80 plant species, but two host strains are recognized based on their association with corn (C-strain) or rice and smaller grasses (R-strain). The population genomics of the United States (USA) fall armyworm remains poorly characterized to date despite its agricultural threat. Results In this study, the population structure and genetic diversity in 55 S. frugiperda samples from Argentina, Brazil, Kenya, Puerto Rico and USA were surveyed to further our understanding of whole genome nuclear diversity. Comparisons at the genomic level suggest a panmictic S. frugiperda population, with only a minor reduction in gene flow between the two overwintering populations in the continental USA, also corresponding to distinct host strains at the mitochondrial level. Two maternal lines were detected from analysis of mitochondrial genomes. We found members from the Eastern Hemisphere interspersed within both continental USA overwintering subpopulations, suggesting multiple individuals were likely introduced to Africa. Conclusions Our research is the largest diverse collection of United States S. frugiperda whole genome sequences characterized to date, covering eight continental states and a USA territory (Puerto Rico). The genomic resources presented provide foundational information to understand gene flow at the whole genome level among S. frugiperda populations. Based on the genomic similarities found between host strains and laboratory vs. field samples, our findings validate the experimental use of laboratory strains and the host strain differentiation based on mitochondria and sex-linked genetic markers extends to minor genome wide differences with some exceptions showing mixture between host strains is likely occurring in field populations.

scholarly journals Functional Importance of Deletion Mutant Genotypes in an Insect Nucleopolyhedrovirus Population

2005 ◽  
Vol 71 (8) ◽  
pp. 4254-4262 ◽  
Author(s):  
Oihane Simón ◽  
Trevor Williams ◽  
Miguel López-Ferber ◽  
Primitivo Caballero
Keyword(s):  
Spodoptera Frugiperda ◽  
Fall Armyworm ◽  
Genotypic Diversity ◽  
Open Reading Frames ◽  
Median Lethal Concentration ◽  
Functional Importance ◽  
Positive Interaction ◽  
Reading Frame ◽  
Genomic Deletions ◽  
Reading Frames

ABSTRACT A Nicaraguan isolate of a nucleopolyhedrovirus (SfNIC) that attacks the fall armyworm, Spodoptera frugiperda, survives as a mixture of nine genotypes (SfNIC A to I) that all present genomic deletions, except variant B (complete genotype). Sequencing of cloned restriction fragments revealed that genotypic variants lack between 5 and 16 of the open reading frames present in a contiguous sequence of 18 kb of the SfNIC genome. The absence of oral infectivity of SfNIC-C and -D variants is related to the deletion of the pif and/or pif-2 gene, while that of SfNIC-G remains unexplained. The presence of open reading frame 10, homolog of Se030, also appeared to influence pathogenicity in certain variants. Previous studies demonstrated a significant positive interaction between genotypes B and C. We compared the median lethal concentration of single genotypes (A, B, C, D, and F) and co-occluded genotype mixtures (B+A, B+D, B+F, A+C, and F+C in a 3:1 ratio). Mixtures B+A and B+D showed increased pathogenicity, although only B+D restored the activity of the mixture to that of the natural population. Mixtures of two deletion variants (A+C and F+C) did not show interactions in pathogenicity. We conclude that minority genotypes have an important influence on the overall pathogenicity of the population. These results clearly demonstrate the value of retaining genotypic diversity in virus-based bioinsecticides.

Concentration–Mortality Response of Mexican Populations Fall Armyworm (Lepidoptera: Noctuidae) to Commercial Formulations of Bacillus Thuringiensis

2021 ◽  
Vol 56 (1) ◽  
pp. 70-83
Author(s):  
María del Carmen Lara-Becerra ◽  
Manuel Alejandro Tejeda-Reyes ◽  
Ángel Lagunes-Tejeda ◽  
Gonzalo Silva-Aguayo ◽  
J. Concepción Rodríguez-Maciel
Keyword(s):  
Bacillus Thuringiensis ◽  
Spodoptera Frugiperda ◽  
Zea Mays L ◽  
Fall Armyworm ◽  
Mortality Response ◽  
Important Pest ◽  
Median Lethal Concentrations ◽  
Lepidoptera Noctuidae ◽  
Laboratory Bioassays ◽  
Mexican Populations

Abstract The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is the most economically important pest of maize (Zea mays L.) grown in Mexico. In order to identify biologically based management tactics for this pest, we determined the concentration–mortality response of 16 S. frugiperda populations collected in Mexico to two commercial formulations of Bacillus thuringiensis Berliner (Bt) (XenTari® [Bt subsp. aizawai] and DiPel® [Bt subsp. kurstaki]; Valent de México SA De CV, Jalisco, México). Laboratory bioassays established median lethal concentrations (LC50s) for each Bt formulation × population combination. We also determined mean larval weight 7 d after exposure and the number of larvae that reached the third instar of development. The populations were susceptible to both Bt formulations but they were, overall, more susceptible to Bt subsp. aizawai (XenTari) than to Bt subsp. kurstaki (DiPel). These results can serve as a reference to detect changes in S. frugiperda response to these Bt commercial products over time.

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