| Abstrakt: |
The management of Asian soybean rust (ASR) involves a combination of cultural and chemical strategies. Phakopsora pachyrhizi-resistant isolates to fungicides have emerged, harboring point mutations in the CYP51, CYTB, and SDH genes. These mutants have advantages in regions extensively utilizing site-specific fungicides. However, the dynamics of selection within a single season remain poorly understood. Thus, this study aimed to investigate the potential selection of mutants following four fungicide applications of commercial mixtures (DMI, QoI, and SDHI), in contrast to untreated control plots. Disease progression and fungicide efficacy were also assessed. In the regions of Arapoti, Castro, Ponta Grossa in Paraná, and Itaberá in São Paulo, mutations on SDH, CYTB, and CYP51 genes were identified, leading to reduced sensitivity to SDHI, QoI, and DMI fungicides. F120L + Y131H mutations in the CYP51 gene were found in Arapoti and Ponta Grossa, and Y131F + K142R + I147T mutations in the CYP51 gene were identified in Itabera-SP. Population from Arapoti had the F129L mutation in the CYTB gene, with a high frequency (> 80%) in treated and untreated plots in Castro and Ponta Grossa. The C-I86F mutation in the SDH gene was detected in all municipalities, exhibiting statistical significance in Arapoti-PR compared to unthread control. In Itaberá, Arapoti, and Ponta Grossa disease severity reached 80% in untreated controls, while fungicides demonstrated efficacies of ranging from 50 to 90%. Importantly, all detected mutations were less frequent in untreated controls, underscoring the significance of anti-resistance management strategies. [ABSTRACT FROM AUTHOR] |
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