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United States Department of Agriculture

Agricultural Research Service

Research Project: SOYBEAN DISEASE AND PEST MANAGEMENT Title: New Legume Hosts of Phakopsora pachyrhizi Identified from Field Studies in Florida

Authors
item Lynch, T - UNIV OF ILLINOIS
item Steinlage, T - UNIV OF ILLINOIS
item Miles, Monte
item Marois, J - UNIV OF FLORIDA
item Wright, D - UNIV OF FLORIDA
item Hartman, Glen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 14, 2008
Publication Date: October 1, 2008
Citation: Lynch, T.N., Steinlage, T.A., Miles, M.R., Marois, J.J., Wright, D.L., Hartman, G.L. 2008. New Legume Hosts of Phakopsora pachyrhizi Identified from Field Studies in Florida. Plant Disease. 92:767-771.

Interpretive Summary: Soybean rust was first reported in the continental United States in November 2004. In 1992, Phakopsora pachyrhizi was reported to infect 86 species of legumes in the Papilionoideae subfamily. On 15 November 2006, 101 species of small-seeded legumes, predominately those found in soybean-growing areas of the United States, were transplanted into a field adjacent to infected soybeans in Quincy, FL. Leaf samples of nine species that had lesions and rust uredinia were confirmed positive for P. pachyrhizi. All are reported as hosts for the first time in the U.S. This information is important for plant pathologists and others interested in the host range of the fungus and the impact this may have on over wintering areas in the south where the host and the pathogen coexist.

Technical Abstract: Soybean rust was first reported in the continental United States in November 2004.In 1992, Phakopsora pachyrhizi Syd. & P. Syd. was reported to infect 86 species of legumes in the Papilionoideae subfamily. On 7 August 2006, 101 species of small-seeded legumes, predominately those found in soybean-growing areas of the United States, were planted into soil-less medium in a rust-free greenhouse in Illinois. On 7 September 2006, seedlings were transplanted into a field adjacent to infected soybeans in a randomized complete block design with three replications at the NFREC in Quincy, FL. On 15 November 2006, plant samples were collected, and leaves were examined using a dissecting microscope for sporulating uredinia. Leaf samples of nine species that had lesions and rust uredinia appearing to be that of P. pachyrhizi were sent to the USDA/APHIS/PPQ/NIS Laboratory, Beltsville, MD for morphological examination and confirmation by polymerase chain reaction using primers specific to P. pachyrhizi. All nine species were confirmed positive for P. pachyrhizi using both methods. These were Cajanus cajan (pigeonpea, PI 520598), Calopogonium caeruleum (jicama, PI 362125), C. mucunoides (calopo, PI 286288), C. mucunoides (calopo, PI 322302), Glycyrrhiza lepidota (American licorice, PI 215213), Medicago sativa subsp. sativa (alfalfa, PI 536536), Neonotonia wightii (PI 284804), Pueraria phaseoloides (tropical kudzu, seed from Guatemala), Teramnus labialis (blue wiss, PI 517204), Trifolium bejariense (Bejar clover, PI 284008). All are reported as hosts for the first time in the U.S. To our knowledge, C. caeruleum, G. lepidota, M. sativa subsp. sativa, P. phaseoloides, T. labialis, and T. bejariense have not previously been reported as hosts of P. pachyrhizi. This also is the first report of Glycyrrhiza and Teramnus genera as hosts of P. pachyrhizi.

Last Modified: 11/23/2014
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