Lack of an Intron in Cytochrome b and Overexpression of Sterol 14 alpha-Demethylase Indicate a Potential Risk for QoI and DMI Resistance Development in Neophysopella spp. on Grapes

Author(s)

Santos, Ricardo F. ^[1] ; Amorim, Lilian ^[1] ; Wood, Ana K. M. ^[2] ; Bibiano, Lillian B. J. ^[1] ; Fraaije, Bart A. ^{[2, 3]}

Affiliation

^[1] Univ Sao Paulo, Luiz de Queiroz Coll Agr, Dept Plant Pathol & Nematol, BR-13418900 Piracicaba, SP - Brazil

^[2] Rothamsted Res, Biointeract & Crop Protect Dept, Harpenden AL5 2JQ, AL - England

^[3] Natl Inst Agr Bot, Cambridge CB3 0LE, Cambs - England

• Document type: Journal article
• Source: PHYTOPATHOLOGY; v. 111, n. 10, p. 1726-1734, OCT 2021.
• Web of Science Citations: 1

Abstract

Asian grapevine leaf rust, caused by Neophysopella meliosmae-myrianthae and N. tropicalis, is often controlled by quinone outside inhibitor (QoI) and demethylation inhibitor (DMI) fungicides in Brazil. Here, we evaluated the sensitivity of 55 Neophysopella spp. isolates to pyraclostrobin (QoI) and tebuconazole (DMI). To elucidate the resistance mechanisms, we analyzed the sequences of the cytochrome b (CYTB) and cytochrome P450 sterol 14 alpha-demethylase (CYP51) target proteins of QoI and DMI fungicides, respectively. The CYP51 expression levels were also determined in a selection of isolates. In leaf disc assays, the mean 50% effective concentration (EC50) value for pyraclostrobin was about 0.040 mu g/ml for both species. CYTB sequences were identical among all 55 isolates, which did not contain an intron immediately after codon 143. No amino acid substitution was identified at codons 129, 137, and 143. The mean EC50 value for tebuconazole was 0.62 mu g/ml for N. tropicalis and 0.46 mu g/ml for N. meliosmae-myrianthae, and no CYP51 sequence variation was identified among isolates of the same species. However, five N. meliosmae-myrianthae isolates grew on leaf discs treated at 10 mu g/ml tebuconazole, and these were further exposed to tebuconazole selection pressure. Tebuconazole-adapted laboratory isolates of N. meliosmae-myrianthae showed an eight- to 25-fold increase in resistance after four rounds of selection that was not associated with CYP51 target alterations. In comparison with sensitive isolates, CYP51 expression was induced in the presence of tebuconazole in three out of four tebuconazole-adapted isolates tested. These results suggest a potential risk for QoI and DMI resistance development in Neophysopella spp. (AU)

• FAPESP's process: 18/25596-7 - Molecular characterization of Plasmopara viticola and Phakopsora meliosmae-myrianthae with different levels of sensitivity to QoI and DMI fungicides in Brazil
• Grantee: Ricardo Feliciano dos Santos
• Support type: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 17/21412-6 - Population structure and sensitivity of Plasmopara viticola and Phakopsora euvitis to fungicides in Brazil
• Grantee: Ricardo Feliciano dos Santos
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 13/24003-9 - Grape diseases: epidemiology, damage assessment and control
• Grantee: Lilian Amorim
• Support type: Research Projects - Thematic Grants