Resistance mechanisms in postharvest fungicides

• Published in: Phytopathology Vol. 100; no. 6; p. S162
• Main Authors: Gisi, U, Sierotzki, H
• Format: Journal Article
• Language: English
• Published: 01.06.2010
• Subjects: Botrytis; Citrus; Fusarium; Glomerella; Helminthosporium; Monilinia; Penicillium; Prunus; Solanum tuberosum
• ISSN: 0031-949X

The most important pathogens attacking fruits like citrus, apples, peaches and potato tubers after harvest include several species of Penicillium, Botrytis, Glomerella, Monilinia, Altemaria, Fusarium and Helminthosporium. A range of fungicide groups are used to control these pathogens such as phenylpyrroles (PPs, fludioxonil), anilinopyrimidines (APs, e.g. pyrimethanil), quinone outside inhibitors (QoIs, e.g. pyraclostrobin, azoxystrobin), and sterol biosynthesis inhibitors (SBIs, e.g. fenhexamid, several azoles). As with older fungicides such as benzimidazoles (MBCs, e.g. thiophanate-methyl), resistance can evolve after intensive use and limit pathogen control to a certain degree. The extent and level of resistance evolution can be assessed using a range of elements including intrinsic and extrinsic fungicide risks, as well as pathogen and agronomic risks. Risk factors are assessed based on molecular, genetic, biochemical, physiological and population aspects. Resistance can be monogenic as in MBCs and QoIs or polygenic as in DMIs. For PPs, resistance is claimed to be linked to os-2 and ABC transporter genes, for APs by two mutations in the cystathionine-g-synthase (cgs) gene. Resistance management should include all available elements including good agronomical practice, limitation of inoculum carry-over from field to packing house, reduction in the number of fungicide treatments and use of mixtures and alternations of fungicides with different modes of action.