Resistance of Fall Armyworm Populations to Bt Proteins in Mexico and Puerto Rico

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Vinodakumargoud Patil

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1. Introduction
2. Material and Methods
3. Results and Discussions
4. Conclusions
5. Elements of resistance management
6. References
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Outline of presentation

 Fall armyworm, Spodoptera frugiperda (J.E. Smith)
(Lepidoptera: Noctuidae) is native to the Americas and is a
major pest in the US, Africa, Australia and Southeast Asia.
 The first report of fall armyworm resistance to Cry1F
occurred in Puerto Rico in populations collected in 2010
and Present study gives high level of Field evolved
resistance to Cry1F and Cry1Ac pyramided Bt-corn hybrids.
 Some pyramided Bt-Corn hybrids containing Cry1A.105
and Cry2Ab2 in addition to Cry1F have been grown in
Puerto Rico from 2018.
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Introduction
Mexico
 In Mexico, Bt-Corn has not yet been approved for commercialization. But, country has experienced the
benefits of Bt & herbicidal tolerant to Cotton and Soyabean herbicide tolerant. But corn is a controversial
crop due to staple food in Mexico.

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Materials and methods
Spodoptera
frugiperda
Mexico
Sinaloa Jalisco Oaxaca
Puerto Rico
Purerto
Rica -Field
Population
Purerto Rica -
Lab
Population
Bt-Proteins
Corteva
Agrisciences
Cry1F Cry1Ac
Bayer Crop
sciences
Cry1A.105 Cry2Ab2
 Field and Laboratory Fall Armyworm Populations  Cry Proteins
General terms
 LC50 Lethal Concentration (50%) Concentration that is lethal to 50% of a population of test animals.
 Reported by mg of toxicant/kg of body weight.
 Smaller the LC50 = Greater toxicity of Chemical/Protein
 Greater the LC50 = lesser toxicity of Chemical/Protein.
 EC50 Effective Concentartion (50%) Causes 50% of the population Exhibit Growth reduction and Weight.

Diet Overlay Bioassay
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To determine the toxicity of Cry proteins following Steps are being used
S.frugiperda artificial diet preparation
Dispensing 1ml of diet into the each well
Specific protein can be used for
Specific insects
Cry1F/Cry1Ac/Cry1A.105/Cry2Ab2
Solidification of Diet and Release Neonates
Observation on 7th Day, Mortality & Growth parameters
Data analysis By SAS
Results LC50 - LC99
Replicated 5times & selecting best
of 3 replications.

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Cry protein concentrations were used in the diet overlay Bioassay

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Mortality response of FAW populations to Bt proteins
57.3

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Effective concentration response of FAW populations to Bt proteins

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Graphical representation of Fall armyworm to different Cry proteins
Jal PR Sus Jal PR
15.3 34
148.2 118
1815
ne
49.7
13.3
172.1
119.2
ne 4.6
201
14.5
273
26.5 29.2 42 174.4
>10,000

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LC50 Sus Popln
LC99 Sus Popln
Dose response of Puerto Rico Population, Fall armyworm to Cry1F

 Bt-Corn producing all Bt proteins has high potential for Fall armyworm control in
Mexico. (Cry1F, Cry1Ac, Cry1A.105 and Cry2Ab2)
 Fall armyworm management in Puerto Rico has been preserved susceptiblelity to
Cry2Ab2 and Cry1A.105 proteins to date. Unfortunately, Cry1F and Cry1Ac
resistance established in Fall armyworm from Puerto Rico Island.
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Conclusion

 Deployment of single toxins like Cry1F expressing Bt-corn hybrids (TC1057).
 Cross-resistance in fall armyworm to Cry1 proteins.
 Bt-crops did not express high doses of the Bt proteins.
 Not following Refuge strategy.
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Factors involved in development of Cry1F resistance

 Application of (IPM) integrated pest management practices.
 Continuing to promote the use of refuge by outreach education program for growers.
 Involving proactive engagement with stakeholders, such as the academia, industry, regulatory
authorities and grower organizations.
 New management strategies are being designed for regional implantation such as Push and Pull
Technology.
 Introduction of Pyramided Bt-crops.
 Crop rotation & Alternate year Fallow periods.
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Elements of resistance management
 Push-pull strategies involve the behavioral manipulation of insect
pests and their natural enemies via the integration of stimuli that
act to make the protected resource unattractive or unsuitable to
the pests (push) while luring them toward an attractive source
(pull) from where the pests are subsequently removed.

 Moreno, R.G., Sanchez, D.M., Blanco, C.A., Chandrasena, D., Difonzo, D., Conner, J., Head, G.,
Berman, K., and Wise. J. (2020) Susceptibility of Fall armyworms (Spodoptera frugiperda J.E.) from
Mexico and Puerto Rico to Bt-Proteins. Insects, 11:831; https://doi:10.3390/insects1112083.
 Borja, M.R., Maciel, J.C.R., Gutiérrez, J.A.U., Aguayo, G.S., Chandrasena, D.I., Bermudez, N.C., and
Storer, N.P. (2020) Baseline of Susceptibility to the Cry1F Protein in Mexican Populations of Fall
Armyworm. Journal of Economic Entomology, 113:390-398; https://doi.org/10.1093/jee/toz280
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Reference

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Resistance of Fall Armyworm Populations to Bt Proteins in Mexico and Puerto Rico

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Resistance of Fall Armyworm Populations to Bt Proteins in Mexico and Puerto Rico