Adaptação de linhagem fúngica ao tebuconazol para o desenvolvimento larval de Scaptotrigona postica

Abstract

Stingless bees establish close associations with microorganisms present within their colonies. Notably, an obligate interaction has been described in which fungi inhabiting brood cells are essential for larval development. In this context, the present study investigated the effects of tebuconazole on fungi associated with Scaptotrigona postica and on in vitro larval development. Microbial isolation from brood combs, larval food, and cerumen, using diferente culture media and recovery strategies, resulted in the retrieval of seven recurrent morphotypes. Monascus pilosus was the predominant isolate (≈ 33% of the evaluated culture plates) and showed optimal growth in the hyperosmotic 30G medium. The fungus exhibited progressive tolerance to tebuconazole, maintaining growth at a concentration of 14.75 μg/ml after adaptive gradient selection. When co-cultured, native and fungicide-exposed strains displayed low competitive interactions. Finally, in vitro larval development assays showed that the presence of tebuconazole at the estimated residual concentration (0.118 μg/mL) was associated with complete larval mortality by day six, regardless of the fungal strain used. In the absence of the fungicide, the adapted M. pilosus strain increased pupation rates by only 4% compared with the control isolate. These findings indicate that, although fungal adaptation is feasible, the resulting tolerance was not sufficient to restore larval development under tebuconazole exposure, highlighting the complexity of interactions among stingless bees, symbiotic microorganisms and fungicides.