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Genetic diversity and population structure of the bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) recently introduced in South America

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Author(s):
Rogério Martins Gonçalves
Total Authors: 1
Document type: Master's Dissertation
Press: Campinas, SP.
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
Defense date:
Examining board members:
Ana Maria Lima de Azeredo Espin; Alberto Soares Corrêa; Vera Nisaka Solferini
Advisor: Thiago de Araújo Mastrângelo; Ana Maria Lima de Azeredo Espin
Abstract

Among the 18 species that comprise the genus Helicoverpa (Lepidoptera: Noctuidae), H. armigera (Hübner, 1808) stands out as the most impactful agricultural pest in the Old World. This species was considered nonexistent in the Americas when, in early 2013, it was identified parasitizing soybean and cotton in Brazil. Subsequently, the record of their occurrence was expanded in the country and also in neighboring countries, leading to agricultural and economic losses. H. armigera is a highly polyphagous species, with more than 180 different host plants. Adult females have high fertility and caterpillars prefer to infest reproductive structures of the plant, directly affecting agricultural production. Individuals of this species can also migrate great distances and are highly resistant to insecticides. In tropical regions, populations produce as many as 11 generations per year. The population size and the number of generations are influenced mainly by the hot climate and the availability of hosts. Optimal conditions can be found in most of the cultivated regions of Brazil. Due to the great morphological similarity, other species from Noctuidae family like Heliothis virescens, Helicoverpa assulta, H. punctigera and H. zea may be mistaken for H. armigera, what compromises pest management policies. Thus, proper identification of the species is essential to agriculture. Beyond economic considerations, we are interested in the comprehension of genetic diversity and population and demographic dynamics in the regions recently invaded of South America. 387 specimens from different localities in South America had a region from mitochondrial gene COI sequenced, of which 266 matched 98-100% with H. armigera reference sequences deposited in public databases. Sequences were aligned with other species of Noctuidae family and the phylogenetic tree was inferred by the following methods: Neighbor-joining, using K2P and p-distance models, Bayesian Inference and Maximum Likelihood Modelling. The COI and Cyt b gene haplotypes were compared with other haplotypes found in other countries around the world, however it a correlation was not observed that could indicate a source of introduction. Haplotypes networks of COI, COII, Cyt b gene and these concatenated genes showed a high genetic diversity, which would not be expected for a population that had recently undergone a bottleneck due to a founder effect. Population parameters showed no structure and haplotypes widely distributed. Demographic parameters indicated a population in expansion. The niche modeling showed that the Northeast and Midwest regions are those with climactic and environmental conditions suitable for H. armigera establishment. This analysis supported the results that indicate that the populations of these regions suffer a more intense expansion and receive a greater number of migrants from other regions. The findings of this study contribute to a better understanding of this species' behavior in the newly invaded American continent and they can support more efficient strategies for control of this costly agricultural pest (AU)

FAPESP's process: 14/10504-9 - Genetic diversity and population structure of the bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) recently introduced in South America
Grantee:Rogério Martins Gonçalves
Support type: Scholarships in Brazil - Master