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United States Department of Agriculture

Agricultural Research Service

Research Project: SOYBEAN DISEASE AND PEST MANAGEMENT

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

Title: First report of soybean rust (Phakopsora pachyrhizi) on Florida beggarweed (Desmodium tortuosum) in Alabama

Authors
item Delaney, M -
item Sikora, E -
item Delaney, D -
item Palm, M -
item Haudenshield, James
item Hartman, Glen

Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: March 1, 2012
Publication Date: September 1, 2012
Citation: Delaney, M.A., Sikora, E.J., Delaney, D.P., Palm, M.E., Haudenshield, J.S., Hartman, G.L. 2012. First report of soybean rust (Phakopsora pachyrhizi) on Florida beggarweed (Desmodium tortuosum) in Alabama. Plant Disease. 96:1374.

Interpretive Summary: Soybean rust, caused by a fungus, was detected on Florida Beggarweed for the first time in Alabama in November, 2009. The pathogen was observed on plants collected from a field at the Wiregrass Research and Extension Center in Headland, Alabama located in the southeast region of the state. Symptoms on leaves were consistent with symptoms of the fungus previously described on soybeans. Symptomatic leaves were analyzed for the fungus using an monoclonal antibody strip test kit and a molecular detection assay. A subsample of 20 plants were positive for P. pachyrhizi. Voucher specimens were deposited in the USDA Agricultural Research Service, National Fungus Collection. This infomration is useful for epidemiologists that are examing the distribution of this fungal pathogen on soybeans and other hosts, and for mycologists that are interested in host ranges of rust pathogens.

Technical Abstract: Soybean rust, caused by the fungus Phakopsora pachyrhizi, was detected on Florida Beggarweed (Desmodium tortuosum) for the first time in Alabama in November, 2009. The pathogen was observed on plants collected from a field at the Wiregrass Research and Extension Center in Headland, Alabama located in the southeast region of the state. Symptoms on leaves were consistent with symptoms of Phakopsora pachyrhizi previously described on soybeans.Sori in leaf spots were observed on the undersurface of the leaves. Urediniospores and paraphyses were observed microscopically and were identified as Phakopsora pachyrhizi. Symptomatic leaves were analyzed for P. pachyrhizi using an Envirologix monoclonal antibody strip test kit at the Auburn University Plant Diagnostic Laboratory. A subsample of 20 plants were positive for P. pachyrhizi. Representative symptomatic leaves were sent to the USDA Molecular Diagnostic Laboratory in Beltsville, Maryland for further confirmation. DNA was extracted from sori aseptically removed from leaves using a Qiagen DNeasy Plant Mini Kit, and amplified with primers Ppa1 and NL4. The resulting partial ITS2 and 28S ribosomal RNA sequences were 100 % identical to GenBank entry DQ354537. Voucher specimens were deposited in the USDA Agricultural Research Service, National Fungus Collection (BPI).

Last Modified: 8/22/2014
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