Micronucleus Induction in Vicia faba Root Tips by Crude Oil-Polluted Soil from Ecuadorian Amazon

In the past four decades, the Amazon rainforest has emerged as a crucial zone for crude oil extraction in the South American region. In the Ecuadorian Amazon rainforest, hydrocarbon blocks (called "bloques") cover vast zones, including agricultural and livestock farms, protected natural regions and the territories of uncontacted indigenous tribes. This study proposes a micronuclei assay on Vicia faba following a 24 h exposure to various soil samples collected from Bloque 57 in Ecuador. Sampling was conducted between the Dayuma and Aguarico zones, approximately 30 km from Nueva Loja city. The research aimed to assess the impact of different soil samples, particularly those from areas affected by crude oil spills, to induce micronuclei and mitotic index changes in V. faba roots. Results: The soil pollution caused by crude oil is not the sole factor contributing to cytotoxicity and genotoxicity in V. faba. Most samples from areas polluted by crude oil outside the small-scale farm showed no significant difference in micronuclei rate compared to negative control and Amazon unpolluted soil. Conversely, samples from the small-scale farm displayed a statistically significant genotoxic effect. Furthermore, samples collected from open-air wastewater pools demonstrated higher levels of cytotoxicity compared to the controls and those from small-scale farms. The mitotic index was lower in seedlings exposed to wastewater in open-air pools, especially for the 20 cm deep samples. This phenomenon could be linked to bitumen-like substances and oils floating on the surface, attaching to the small roots and causing suffocation.