Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/31/2007
Publication Date: 8/31/2007
Citation: Glynn, N.C., Comstock, J.C. 2007. Molecular identification of orange rust (Puccinia kuehnii) in Florida. Meeting Abstract. Interpretive Summary:
Technical Abstract: Sugarcane (Saccharum spp.) can suffer economic losses due to disease caused by either of two Puccinia species. Common or brown rust caused by Puccinia melanocephala has been a prevalent disease in Florida since the late 1970’s however until recently the Florida industry was considered free from P. kuehnii, the causal agent of orange rust. Brown rust and orange rust favor different environmental conditions. The most severe infections from brown rust typically take place during the cool periods of the growing season when the crop is between 3 and 6 months in age. In contrast, orange rust infection is favored by warmer conditions. Recent reports in June 2007 of brown rust pustules showing atypical morphology and orange coloration on sugarcane leaves of two leading commercial sugarcane varieties (CP 72-2086 and CP 80-1743) were investigated using molecular techniques. Spores were harvested from infected leaves and DNA was extracted using standardized procedures. A portion of rDNA incorporating the 18S, ITS1, 5.8S, ITS2 and 28S regions was amplified using previously described primers in conserved parts of the 18S and 28S genes. The amplified fragments were isolated and sequenced and the sequences compared to those within the National Center for Biotechnology Information (NCBI) database by BLAST analysis. The sequences from each sample matched those for P. kuehnii that were already in the database and showed poor homology with sequences of the same region taken from P. melanocephala. Taken together this information confirms that the atypical rust symptoms observed during a period when brown rust pustules are not usually prevalent were indeed orange rust caused by P. kuehnii. This is the first confirmed report of orange rust in the Western hemisphere.