Print version ISSN 0120-9965
ARGEL, Luz et al. Molecular and phenotypic characterization of the resistance level to fenamidone in Peronospora sparsa isolates. Agron. colomb. [online]. 2007, vol.25, n.1, pp. 149-159. ISSN 0120-9965.
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 monitor QoI fungicide sensitivity in P. sparsa populations in the rose growing regions of Colombia.
Keywords : cytochrome b; EC50; QoI fungicides; Downy mildew; punctual mutation.