Hitching a Ride: Examining the Ability of a Specialist Baculovirus to Translocate through Its Insect Host’s Food Plant

Plant vascular systems can translocate the entomopathogen Bacillus thuringiensis from the soil into plant tissues. However, whether other soil dwelling entomopathogens utilize plant vascular tissue for movement has not yet been fully explored. We used Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) to evaluate whether baculoviruses, a common entomopathogen and bioinsecticide, can be transported through the plant vascular pathways of Zea mays. We found that our treatments did not allow a sufficient virus translocation into the plant to induce a lethal infection in insects, which was confirmed by a molecular analysis. While other entomopathogens translocate, baculoviruses may not be one of them.

Sequencial passages of the multiple nucleopolyhedrovirus of Anagrapha falcifera(Kirby) (Lepidoptera: Noctuidae) (AfMNPV) in Spodoptera cosmioides (Walker) (Lepidoptera, Noctuidae)

O objetivo deste trabalho foi avaliar os efeitos de múltiplas passagens do nucleopoliedrovírus de Anagrapha falcifera (AfMNPV) na biologia de lagartas de S. cosmioides, em diferentes momentos de infecção, e as alterações histológicas que o vírus poderia causar no intestino médio da lagarta, buscando correlacionar os efeitos histopatológicos e a eficácia deste vírus, como um potencial controle biológico desta praga. As lagartas foram infectadas com sete dias de desenvolvimento, utilizando três passagens diferentes do AfMNPV em S. cosmioides (F1, F4 e F7, sendo a primeira, quarta e sétima passagens, respectivamente) e o tratamento controle. Foram realizados, concomitantemente, ensaios de biologia, comparados com os mesmos tratamentos, para analisar o comportamento e mortalidade das lagartas. A morfologia do intestino médio foi comparada entre as lagartas infectadas e as não infectadas. Os tubos digestivos foram coletados com 24, 72 e 144 horas de infecção (20 tubos/tratamento/tempo de infecção). Após a coleta, os tubos foram fixados em Karnovsky, processados, corados com Hematoxilina-Eosina e analisados ao microscópio de luz. Os resultados da biologia dos tratamentos F4 e F7, mostraram uma redução drástica na locomoção e alimentação das lagartas, a partir do quarto dia pós-infecção e maior taxa de mortalidade cumulativa, em relação ao controle e F1. Morfologicamente, todos os tratamentos causaram alterações no intestino médio das lagartas de S. cosmioides, nos três tempos de infecção, sendo que as maiores alterações ocorreram no epitélio. O AfMNPV, nas três passagens testadas em S. cosmioides, provocou alterações comportamentais e morfológicas no intestino médio, indicando que pode ser um promissor agente de controle biológico desta praga.

Genome Sequence of a Spodoptera frugiperda Multiple Nucleopolyhedrovirus Isolated from Fall Armyworm (Spodoptera frugiperda) in Nigeria, West Africa

We report the entire genome sequence of an isolate of Spodoptera frugiperda multiple nucleopolyhedrovirus from Nigeria, West Africa. The genome is 132,710 bp long and contains 144 open reading frames. The GC content is 40.3% and, based on baculovirus species demarcation criteria, the isolate belongs to the species Spodoptera frugiperda multiple nucleopolyhedrovirus .

Host-virus and virus-virus interactions in broad host range alphabaculoviruses: implications for the development of virus-based insecticides

This thesis examined the insecticidal potential of the broad host range baculovirus Mamestra brassicae multiple nucleopolyhedrovirus (MbMNPV), and this interaction with Helicoverpa armigera multiple nucleopolyhedrovirus (HaMNPV) during the coinfection of a shared host. The results provide greater understanding of host-virus and virus-virus interactions in broad host range alphabaculoviruses that should help define effective strategies for pest control in field and greenhouse crops. First, the insecticidal activity and stability of the two closely related alphabaculovirus isolates, HearMNPV and MbMNPV derived from the commercial bioinsecticide Mamestrin®, were evaluated in a permissive (Spodoptera exigua) and a semi-permissive host (Spodoptera littoralis). The genetic structure of MbMNPV derived from the biological insecticideMamestrin® was then studied with the aim of assessing the insecticide properties of the genotypic variants comprised this wild-type isolate. Finally, interactions between two phylogenetically closely related viruses during coinfection of a shared host were analysed. In conclusion, the results obtained in this thesis contribute to a better understanding of the interactions between viruses and their hosts, which can contribute to the development of baculovirus-based insecticides and to design of effective strategies for the control of lepidopteran pest complexes.