Characterization of resistance to teflubenzuron in host-strains of Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae)

Author(s)

Juliana Gonzales Rodrigues

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2021-09-03

Examining board members

Celso Omoto; Oderlei Bernardi; Karina Lucas da Silva Brandão; Fernando Luis Consoli

• Advisor: Celso Omoto

Abstract

The knowledge of intraspecific variability in insect pest populations is crucial for implementing effective integrated management programs, mainly for polyphagous pests. The impact of the differentiation of Spodoptera frugiperda (J.E. Smith) in two host-associated strains named rice and corn strains, as well as hybrids resulting from the interstrain matings, on the management of this pest needs a better understanding. Therefore, the objective of this research was to verify if the host-associated strains of S. frugiperda can influence the resistance evolution to insecticides, mainly to teflubenzuron. Studies were conducted to (i) characterize the susceptibility of the host-strains of S. frugiperda to different insecticides (chlorantraniliprole, chlorfenapyr, chlorpyrifos, indoxacarb, lambda-cyhalothrin, methomyl, methoxyfenozide, spinetoram, teflubenzuron and thiodicarb); (ii) select and characterize the resistance to teflubenzuron in host-strains of S. frugiperda; (iii) evaluate the fitness cost associated with teflubenzuron resistance in host-strains of S. frugiperda; and (iv) investigate the expression pattern of genes potentially related to the mechanism of resistance to teflubenzuron in host-strains of S. frugiperda. The host-strains of S. frugiperda used in this study were isolated from a population of S. frugiperda collected on cornfields in Rio Grande do Sul State using mitochondrial (COI) and nuclear (Tpi) DNA genetic markers. Only individuals from corn (77%) and hybrid (23%) strains were found in this population. The corn strain presented higher susceptibility than the hybrid strain to most of the insecticides tested, except for indoxacarb and spinetoram. There was selection response for resistance to teflubenzuron in both corn and hybrid strains, with LC50 for the hybrid strain approximately 5 times higher than for the corn strain. The fitness cost analysis, based on the fertility life table parameters, indicated that there is a fitness cost associated to teflubenzuron resistance in corn and hybrid strains of S. frugiperda and the host-strain factor did not influence the magnitude of the fitness cost. The expression analysis of genes potentially related to the teflubenzuron resistance in S. frugiperda indicated that the hybrid and corn host-strains presented distinct gene expression patterns to most of the evaluated transcripts; such as the cuticular proteins RR-1 and RR-2 were superexpressed in the teflubenzuron-resistant hybrid host-strain and the CYPs enzymes were superexpressed in the teflubenzuron-resistant corn strain. The results obtained here reinforce the relevance of identification of the host-strains of S. frugiperda to characterize the susceptibility to insecticides and to design resistance management strategies. (AU)

• FAPESP's process: 19/06215-5 - Host-associated races of Spodoptera frugiperda (Lepidoptera: Noctuidae) and their implications to the insecticide resistance management
• Grantee: Juliana Gonzales Rodrigues
• Support Opportunities: Scholarships in Brazil - Master