Molecular and phenotypic characterization of the resistance level to fenamidone in Peronospora sparsa isolates

• Published in: Agronomía colombiana 2007-06 (1)
• Main Authors: Argel, L.E, Marín, M, Cotes, J.M, Jaramillo, S, Guzmán, E
• Format: Article
• Language: Spanish
• Subjects: CITOCROMO B; CYTOCHROME B; DOWNY MILDEW; EC50; FUNGICIDAS; PERONOSPORA; PUNCTUAL MUTATION; QOI FUNGICIDES
• ISSN: 0120-9965

El Mildeo velloso es uno de los mayores limitantes del cultivo de la rosa en Colombia. Esta enfermedad es causada por el Oomycete holobiótrofo Peronospora sparsa que fue detectado en la década de 1970 en la Sabana de Bogotá. En los últimos años su efecto negativo sobre la floricultura aumentó conduciendo a los cultivadores al empleo excesivo de fungicidas con acción sistémica, muchos de los cuales no cuentan con estudios de líneas base de sensibilidad ni con el diseño de estrategias anti-resistencia apropiadas. A fin de determinar el grado de sensibilidad de diez aislamientos de P. sparsa al fungicida fenamidone, representante del grupo de resistencia cruzada QoI, se realizaron pruebas de sensibilidad in vitro y evaluaciones moleculares. Los resultados muestran que este patógeno presenta un alto grado de sensibilidad a dicha molécula (EC50 promedio: 0,51 mg L-1) y que no hay evidencia de la presencia de las mutaciones puntuales G143A y F129L asociadas con fenotipos resistentes a QoI. Este estudio aporta las bases para el desarrollo de una metodología de detección molecular de individuos con resistencia a fungicidas QoI que puede ser utilizada para monitorear las poblaciones del patógeno en nuestro medio Rose downy mildew caused by Peronospora sparsa is a disease of increasing importance for the Colombian flower industry. The disease was first reported in the 1970's and, during the last years, its aggressiveness has increased dramatically. This has meant that an increasing and unacceptable number of fungicide applications are required to control it. This situation has a negative impact on the environment and public health, and requires a program to manage fungicide resistance, including participation of flower growers, fungicide companies, government agencies, and research institutions. The aim of this study was to build up a baseline of sensitivity of P. sparsa isolates to fenamidone, a systemic QoI fungicide, in order to support chemical strategies used to control P. sparsa, and specifically those directed to avoid a loss of sensitivity to these fungicides. The results were linked to the presence of point mutations in the cytochrome b gene, which have previously been linked to resistance to these fungicides. Fungicide evaluations showed a high level of sensitivity of P. sparsa isolates to fenamidone (EC50: 0.51 mg L-1), which was linked to the absence of point mutations G143A and F129L in the cytochrome b gene. A test is currently being designed to monito