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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #204687
Title: Late Season Occurrence of Soybean Rust Caused by Phakopsora pachyrhizi on Soybean in Illinois

Author
item Hartman, Glen
item HINES, R - UNIVERSITY OF ILLINOIS
item FAULKNER, C - UNIVERSITY OF ILLINOIS
item LYNCH, T - UNIVERSITY OF ILLINOIS
item PATAKY, N - UNIVERSITY OF ILLINOIS

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2006
Publication Date: 4/15/2007
Citation: Hartman, G.L., Hines, R.A., Faulkner, C.D., Lynch, T.D., Pataky, N. 2007. Late Season Occurrence of Soybean Rust Caused by Phakopsora pachyrhizi on Soybean in Illinois. Plant Disease. 91(4):466-466.

Interpretive Summary: Soybean rust, first reported in the continental United States in Louisiana in 2004, is the most important foliar disease of soybean, worldwide. On 10 October 2006, 20 soybean leaflets from 20 different plants at physiological maturity growth stage were arbitrarily collected in research plots near Glendale, Illinois at the University of Illinois Dixon Springs Agricultural Center in Pope County. Tan angular lesions, 2 to 4 mm in diameter were observed on the lower leaf surfaces of two of the 20 leaflets. Within these lesions, there was one uredinum on one leaflet and four on the other leaflet exuding hyaline, echinulate urediniospores (20 x 25 um). Identificaion by morphological examination and by molecular techniques confirmed the presence of rust fungus. This is believed to be first report of the fungus, causing soybean rust, infecting plants in Illinois. This information is important to other soybean pathologists, and scientists involved in forecasting and modeling disease epidemics.

Technical Abstract: Soybean rust, first reported in the continental United States in Louisiana in 2004, is the most important foliar disease of soybean, worldwide. On 10 October 2006, 20 soybean leaflets from 20 different plants at physiological maturity growth stage were arbitrarily collected in research plots near Glendale, Illinois at the University of Illinois Dixon Springs Agricultural Center in Pope County, and sent by overnight courier. On 11 October, leaflets were examined with a dissecting microscope at the Soybean Disease Laboratory at the National Soybean Research Center, then at the Plant Disease Clinic, University of Illinois. Tan angular lesions, 2 to 4 mm in diameter were observed on the lower leaf surfaces of two of the 20 leaflets. Within these lesions, there was one uredinum on one leaflet and four on the other leaflet exuding hyaline, echinulate urediniospores (20 x 25 um). On 11 October 2006, these leaflets were sent by overnight courier to the USDA/APHIS/PPQ/NIS Laboratory, Beltsville, MD Plant Disease Clinic for identificaion by morphological examination and by using polymerase chain reaction using primers specific to Phakopsora pachyrhizi. Both tests confirmed the presence of P. pachyrhizi. The 18 leaflets that did not have sporulating pustules on 11 October were incubated in the laboratory for 5 days at near 100% relative humidity. Following incubation, nine leaflets were observed to have uredinia exuding urediniospores with a range of one to 43 uredinia per leaflet. These results indicate that incubation may be necessary to maximize the potential to observe uredinia exuding urediniospores. This is believed to be first report of the fungus, P. pachyrhizi, infecting plants in Illinois.