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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #248324
Title: First Report of Soybean Rust, Caused by Phakopsora pachyrhizi, on Kudzu (Pueraria montana var. lobata) in Illinois

Author
item BRADLEY, CARL - University Of Illinois
item HINES, RON - University Of Illinois
item Haudenshield, James
item Hartman, Glen

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2010
Publication Date: 4/1/2010
Citation: Bradley, C., Hines, R., Haudenshield, J.S., Hartman, G.L. 2010. First Report of Soybean Rust, Caused by Phakopsora pachyrhizi, on Kudzu (Pueraria montana var. lobata) in Illinois. Plant Disease. 94:477.

Interpretive Summary: Soybean rust, caused by Phakopsora pachyrhizi, was first observed on soybean in the continental United States in Louisiana in 2004, and on kudzu in the United States in 2005. Kudzu is a leguminous weed that is prevalent in the southern United States with its range extending as far north as Illinois. In October 2009, a kudzu patch located in Pulaski County in southern Illinois, was found to have soybean rust based on microscopic and non-microscopic methods using specific proteins and nucleic acid techniques. This is the first observation of the disease on kudzu in the state. This report confirms that at least some kudzu plants in Illinois, are susceptible to soybean rust, and that latent kudzu infection may exist without outward signs of the fungus. To date, this is the most northern observation of soybean rust on kudzu in North America. It is unknown what role, if any, Illinois kudzu will play in the epidemiology of soybean rust in the state. Since kudzu tops die after the first frost, there is no expectation of P. pachyrhizi to overwinter in Illinois, on kudzu as it does in some states adjacent to the Gulf of Mexico.

Technical Abstract: Soybean rust, caused by Phakopsora pachyrhizi, was first observed on soybean (Glycine max) in the continental United States in Louisiana in 2004, and on kudzu (Pueraria montana var. lobata) in the United States in 2005. Kudzu is a leguminous weed that is prevalent in the southern United States with its range extending northward into other states including Illinois. In October 2009, a kudzu patch located in Pulaski County in southern Illinois, was investigated for the presence of soybean rust. Leaflets were collected, and the abaxial sides of leaflets were evaluated visually for the presence of uredinia under a dissecting microscope at X100. Uredinia and urediniospores were found on two leaflets (out of 15 collected leaflets total). Urediniospores were hyaline, echinulate, and measured 20 × 25 µm. Based on the uredinia and urediniospores, the disease was identified as soybean rust caused by P. pachyrhizi. To confirm the identification, one leaflet with pustules was assayed with a Soybean Rust QuickStix Diagnostic Kit, and DNA was extracted from the other leaflet with uredinia for confirmation by Quantitative-PCR (Q-PCR) using primers and probe specific to P. pachyrhizi and P. meibomiae. Both the QuickStix Diagnostic Kit and the Q-PCR confirmed the diagnosis as soybean rust caused by P. pachyrhizi. Q-PCR also suggested the presence of a non-sporulating latent rust infection on the same kudzu leaflet at the margin on the opposite side of the midrib. Soybean rust first was confirmed on soybean in Illinois in 2006, but this is the first observation of the disease on kudzu in the state. This report confirms that at least some kudzu plants in Illinois, are susceptible to soybean rust, and that latent kudzu infection may exist without outward signs of the fungus. To date, this is the most northern observation of soybean rust on kudzu in North America. It is unknown what role, if any, Illinois kudzu will play in the epidemiology of soybean rust in the state. Since kudzu tops die after the first frost, there is no expectation of P. pachyrhizi to overwinter in Illinois, on kudzu as it does in some states adjacent to the Gulf of Mexico.