Identification of QoI-Resistant Isolates of the Banana Pathogen Pseudocercospora fijiensis in Mexico

Black Sigatoka disease is a significant threat to banana (Musa spp.) fruit yield and quality. For the control of the fungal pathogen, Pseudocercospora fijiensis, producers currently rely on fungicides such as Quinone outside Inhibitor (QoI). In this study, we examined the resistance status of P. fijiensis to QoI fungicides using 80 isolates from 24 localities in the main banana-producing areas of Mexico (Colima, Michoacán, Tabasco and Chiapas). Resistance was evaluated using the RFLP-PCR mutation assay on Cytochrome b gen (Cytb). The results showed the G143A mutation in three isolates from Chiapas, indicating a relatively low mutation frequency in the sampled areas, where additionally, a microplate bioassay confirmed the resistance to fungicides. We also evaluated the genetic structure and differentiation among the sampled populations, detecting differences between populations within each region and among all populations. Furthermore, our analysis revealed shared haplotypes between resistant populations in Chiapas and nonresistant populations in Michoacán. These findings provide valuable insight into the resistance status of P. fijiensis to QoI fungicides in Mexico and serve as foundation for the development of strategies to manage strobilurin resistance in the country. Overall, this study highlights the importance of monitoring and implementing effective management practices to mitigate the spread of resistant strains.