First detection of Phakopsora pachyrhizi on Jicama in the United States and on Florida beggarweed in Alabama

Soybean Rust, caused by Phakopsora pachyrhizi, was detected on Jicama (Pachyrihius erosus) for the first time in the United States in November, 2009. The pathogen was also detected on Florida beggarweed (Desmodium tortuosum) for the first time in Alabama Phakopsora pachyrhizi was observed on a potted Jicama plant grown outdoors in a residential area, as well as in a demonstration plot at Auburn University. Symptoms appeared on the upper leaf surface as chlorotic isolated areas near the leaf edge on leaves in the lower plant canopy. Symptoms on the lower leaf surface exhibited brown lesions and produced volcano-shaped pustules with urediniospores that were characteristic of Phakopsora sp. Pustules and uredinospores were pale tan in color. Leaves expressing disease symptoms of were analyzed using an Envirologix monoclonal antibody test kit at the Auburn Plant Diagnostic Laboratory. Symptomatic plant tissue was also sent to the USDA National Identification Services Laboratory in Beltsville, MD for further confirmation. The fungal structures present were confirmed to be Phakopsora sp. The samples and forwarded to the USDA National Plant Germplasm and Biotechnology Laboratory for DNA testing and confirmed as P. pachyrhizi. Symptomatic tissue obtained from Florida beggarweed collected in Headland, Alabama was submitted for identification in the same manner. To our knowledge this is the first report of the disease on Jicama in the United States and on Florida beggarweed in Alabama.