The dual nature of Metarhizium: integrating endophytic plant benefits and entomopathogenic pest control

• Ano de defesa: 2025
• Autor(a) principal: Martins, Jéssica Letícia Abreu
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Fungos entomopatogênicos - Controle biológico; Plantas - Doenças e pragas - Controle integrado; Sustentabilidade; CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::ENTOMOLOGIA AGRICOLA
• Link de acesso: https://locus.ufv.br/handle/123456789/34928; https://doi.org/10.47328/ufvbbt.2025.257

Entomopathogenic fungi perform important functions in the ecosystem, being able to act as decomposers of organic matter, and plant growth promoters, in addition to their potential to control insects. Because they are highly diverse organisms, they can establish themselves in equally distinct systems and can occur naturally in soils in natural or highly managed environments, as is the case with crops. Considering the different compositions of the environment they inhabit, these microorganisms often need to adapt to stressful situations, especially in high temperatures and UV radiation. In this way, fungi that have multiple life cycles end up obtaining adaptive advantages, as they can remain in the environment for longer periods, effectively colonizing insects, associated with corpses, and even living in symbiosis with plants. Some of the classic examples of multifunctional organisms are fungi of the genus Metarhizium, which have already shown themselves capable of associating with plants from different cultures as endophytes. When this relationship occurs, these fungi become capable of manipulating direct and indirect defenses, promoting, for example, the production of secondary metabolites or even fungal toxins capable of reducing insect herbivory. It is even known that the fungus can relocate these defenses to specific organs of the plant, depending on the attack of the pests associated with them. Furthermore, there are still studies that explore the ability of these microorganisms to modulate the production of volatiles in plants, promoting attraction or repellency not only of herbivores but also of potential predators capable of controlling pests. In this work, we began to explore the fungal composition of soils from coffee cultivation systems in the Cerrado Mineiro, under diversified systems (i.e., with the insertion of multifunctional plants) and under conventional crops where monoculture was established. The isolates used for molecular characterization came from a pre-established system in 2019, with three samplings carried out until 2021. Although we did not find significant differences in the composition of fungal genera in both systems, we noticed that the dominant genus was Metarhizium, possibly due to its previously mentioned high adaptability characteristics. Therefore, we chose to evaluate in Chapter II the effect of the species M. roberts ii and M. brunneum on the control of the coffee leaf miner (Leucoptera coffeella), with their inoculation in coffee seeds treated with fungicides. We observed that these fungi were able to prolong the life cycle of insects, promoting a reduction in the total number of individuals. Furthermore, they also reduced the number of insects in the second generation, in addition to promoting the growth of coffee plants. Given these results, we also decided to evaluate in Chapter III the effects of this group of microorganisms on a hemimetabolous pest, a pest of a short-cycle crop. We then chose whiteflies (Bemisia tabaci) and cotton plants, and inoculated M. anisopliae by seed inoculation and also by drench in the soil. We observed a reduction in the number of insect eggs and adults when they fed on plants inoculated via seeds, in addition to a greater number of leaves in cotton plants that were subjected to the same treatment. To begin exploring higher trophic levels, we also carried out olfactometer choice experiments with the whitefly and its predator, the ladybug Hippodamia convergens. Our results demonstrated a repellency effect when subjected to the choice of plants inoculated via seed, and a predator attraction effect was observed with the same treatment. In this way, our work seeks to explore the potential benefits of using Metarhizium for sustainable pest management, considering its insect control potential and its endophytic action, which has also been shown to be beneficial for plants. Keywords: entomopathogenic fungi; sustainable management ; biological control.