Scanning electron microscopy of grape downy meldew fungus which resisted to some fungicides
1987
Sudawan Yoojinda (Kasetsart Univ., Bangkok (Thailand). Plant Pest Clinic and Quarantine Unit Central Laboratory and Greenhouse Complex) | Vichai Korpraditskul
Scanning electron microscopy (SEM) applied to study the resistance of grape downy mildew fungus (Plasmopara viticola) to fungicides, metalaxyl and Ridomil MZR, was repported. Several isolates of P. viticola with the different spray programs with fungicide, metalaxyl, from two separate vineyards in Ratchaburi and Samutsakorh Provinces were collected and used in this study. Each of the fungal isolates was induced sporulation by incubating the infected leaves under high relative humidity at 20 % for 20 hr. and spores were harvested and suspended in sterile water. SEM samples were prepared from healthy grape leaves which were previously treated with the different concentration of metalaxyl (1, 10 and 100 ppm) and Ridomil MZR (18, 180 and 1800 ppm). Afterward the treated leaves were inoculated with fungus spores, incubation, tissue saples from inoculated area were cut, fixed and processed as general procedure of SEM sample preparation, and examined with a JEOL JES CF-35 scanning electron microscope. Our data showed that the metalaxyl exposed P. viticola was able to infect and sporulate on the metalaxyl treated leaves but not on the Ridomil MZR-treated leaves. The technique is simple and combines the advantages of great depth of focus and high resolution of the SEM.
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