An insect-parasitic fungus system do study coinfections

• Ano de defesa: 2024
• Autor(a) principal: Costantin, Eduardo Carlos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Coinfecção; Relação hospedeiro-parasito; Nutrição; Temperatura; Pragas - Controle biológico; CIENCIAS AGRARIAS
• Link de acesso: https://locus.ufv.br/handle/123456789/32410; https://doi.org/10.47328/ufvbbt.2024.213

Coinfections occur when two or more parasites concurrently infect the same host, and they are a widespread phenomenon in nature. With significant consequences for host-parasite interactions, coinfections can dramatically alter the severity and epidemiology of a disease, the fitness of the organisms involved, and the evolution of the parasites’ virulence. In this thesis, we propose a study system to investigate coinfections, their outcomes and their environmental modulators. This system is composed of two parasitic fungi – Beauveria bassiana and Metarhizium anisopliae – and the coleopteran host Tenebrio molitor. These fungi have similar infection mechanisms and host exploitation strategies, allowing us to investigate coinfections while diminishing the influences of parasite identity and host- exploitation strategy as variables. In the first chapter, we establish the study system and investigate the effects of characteristics of infection on coinfection outcomes. We find that coinfections did not change virulence towards the host, and when both fungi successfully sporulated on the host's body, the number of spores produced was drastically reduced. We also showed that the location of infection changed the percentage of hosts colonized for both fungi and that the first parasite to arrive dominated the infection process. In the second chapter, we explore the effect of host nutrition on single and coinfections. Host diet has limited impacts on coinfection and parasite fitness, but influences host mortality. A high protein diet is a better substrate to fight fungal infections compared to a high-carbohydrate diet, contradicting prior evidence found in hemimetabolous insects. In the third chapter, we investigate the role of temperature. Higher temperatures diminish the dominance of the most competitive fungus, Beauveria. On the host side, higher mortality occurred within the optimum temperature range for the parasite (~26°C). Our results support the adoption of this model system to study coinfections. This system have allowed us to test the effect of environmental factors and variables related to the process of infection on coinfection. This knowledge can be used to understand the dynamics of coinfection, and to identify variables that could be considered in other biological systems. Additionally, elucidating the interaction patterns between Beauveria bassiana and Metarhizium anisopliae will contribute to increasing the efficiency of entomopathogenic fungi in agroecosytems. Keywords: Coinfections; Host-Parasite Interactions; Nutrition; Temperature; Biological control.