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Polymerase Chain Reaction Assays for the Detection and Discrimination of the Soybean Rust Pathogens Phakopsora pachyrhizi and P. meibomiae

February 2002 , Volume 92 , Number  2
Pages  217 - 227

Reid D. Frederick , Christine L. Snyder , Gary L. Peterson , and Morris R. Bonde

U.S. Department of Agriculture-Agricultural Research Service, Foreign Disease-Weed Science Research Unit, 1301 Ditto Avenue, Fort Detrick, MD 21702

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Accepted for publication 14 October 2001.

Soybean rust occurs in Australia and many countries throughout Africa, Asia, and South America. The causal agents of soybean rust are two closely related fungi, Phakopsora pachyrhizi and P. meibomiae, which are differentiated based upon morphological characteristics of the telia. Determination of the nucleotide sequence of the internal transcribed spacer (ITS) region revealed greater than 99% nucleotide sequence similarity among isolates of either P. pachyrhizi or P. meibomiae, but only 80% sequence similarity between the two species. Utilizing differences within the ITS region, four sets of polymerase chain reaction (PCR) primers were designed specifically for P. pachyrhizi and two sets for P. meibomiae. Classical and real-time fluorescent PCR assays were developed to identify and differentiate between P. pachyrhizi and P. meibomiae. Identification of P. pachyrhizi from infected soybean leaves using the real-time PCR assay will allow for more rapid diagnoses.

The American Phytopathological Society, 2002