Haiko Enok Sawazaki, Luiz Alexandre Nogueira de SÃÆá, Cassiara Regina N. C. B. GonÃÆçalves, Renato Ferraz de Arruda Veiga and Carlos Augusto Colombo
Aiming at optimizing the diagnosis of major sugarcane diseases by PCR, primers were developed (scald, orange rust) and amplified fragments according to the literature were used as positive control, such as those caused by: 1 - Bacteria, (ratoon stunting and leaf scald) 2 - Viruses, (yellow leaf, mosaic, mosaic streak and fijivirus) 3-Fungus, (smut, orange rust and curvularia). For diseases with long latency period (leaf scald, ratoon stunting, yellow leaf, mosaic, fijivirus, smut and orange rust), primers were designed for real time PCR. For testing, infected leaves, fungal colonies, amplified DNA fragment or 40 seedlings were used. Real time PCR analyses have enabled the detection of sugarcane samples with highest dilution of DNA. The pair of primers designed for orange rust was more specific. The pair of primers designed for scald, apparently was not able to distinguish only bacteria of the genus Erwinia, whereas the primers described in the literature were observed amplify others genera, such as Xanthomonas, Pseudomonas, Erwinia, Stenotrophomona and Pantoea. The three strains of the fungus curvularia, found in sugarcane, resembled more to the species C.cymbopogonis, C.geniculata, C.sp. Of the 28 primer pairs tested, the best were shown for each of the disease-causing agent.
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