Disentangling the role of the rhizobacterium <i>Azospirillum brasilense</i> on <i>Zea</i> spp. defenses against <i>Spodoptera frugiperda</i> (Lepidoptera: Noctuidae)

• Ano de defesa: 2026
• Autor(a) principal: Cabral, Isabella Rubio
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertacoes da USP; Universidade de São Paulo; Escola Superior de Agricultura Luiz de Queiroz
• Palavras-chave em Português: Teosinto; <i>Aleiodes ceres</i>; Interações multitróficas; Milho; Rizobactéria promotora de crescimento; Teosinte; Plant-growth promoting rhizobacteria; Multitrophic interactions; Maize
• Link de acesso: https://teses.usp.br/teses/disponiveis/11/11146/tde-11052026-104422/

Interactions between plants and soil-dwelling organisms play a central role in shaping both above- and belowground ecological communities. These interactions are further influenced by plant domestication, which can alter rhizosphere microbial assembly and function, with cascading effects on plant phenotypes and interactions across higher trophic levels. Although numerous studies have examined the influence of beneficial microbes on plant defenses against herbivores, the effects of the plant growthpromoting rhizobacterium (PGPR) <i>Azospirillum brasilense</i> on maize and its wild relatives remain poorly understood, particularly within a multitrophic context. In this dissertation, we examined the cascading effects of the association between <i>A. brasilense</i>, cultivated maize (<i>Zea mays</i>), and the wild relative <i>Zea luxurians</i> on the herbivore <i>Spodoptera frugiperda</i> and its larval parasitoid </i>Aleiodes ceres</i>. Specifically, we evaluated how PGPR inoculation influences plant defense-related traits, herbivore performance and behavior, parasitoid attraction, and plant volatile organic compound emissions. Across both maize and teosinte, inoculation with <i>A. brasilense</i> enhanced fall armyworm larval performance, indicating that microbial associations can increase host suitability for herbivores. At the same time, parasitoids exhibited stronger attraction to inoculated plants, demonstrating that PGPR-mediated changes can also enhance indirect plant defenses. In maize, PGPR inoculation reduced oviposition by adult moths under no-choice conditions, whereas oviposition preference in <i>Z. luxurians</i> was not affected by microbial association. These patterns were supported by qualitative shifts in plant volatile emissions, suggesting that rhizobacterial inoculation modulates signaling pathways involved in plant-insect interactions. Contrary to expectations based on wild ancestry, <i>Z. luxurians</i> did not exhibit enhanced resistance to fall armyworm attack in the absence of microbial association. Collectively, these results highlight the context-dependent nature of plant-microbe-insect interactions and underscore the ecological relevance of belowground symbionts in shaping both direct and indirect plant defenses in domesticated and wild systems.