Submitted to: Southern Soybean Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2011
Publication Date: 3/10/2011
Citation: Rush, T.A., Schneider, S.W., Aime, M.C., Hartman, G.L. 2011. Assessing the Validity of Diagnostic Quantitative PCR Assays for Phakopsora pachyrhizi and P. meibomiae. Southern Soybean Conference Proceedings. Penasacola, FL, March 9-10, 2011, CD ROM. Interpretive Summary:
Technical Abstract: There are 123 confirmed species in the genus Phakopsora worldwide, with 19 species reported in the continental United States. In 2002, a quantitative PCR (qPCR) diagnostic assay was developed by Frederick et al. that has been used for detecting Phakopsora pachyrhizi in spore trapping studies. Based upon these assays, spores of P. pachyrhizi were reported in Ohio and other states where soybean rust was never found. These reports may be based upon false positives. False positives are problematic because they may lead to unnecessary fungicide applications when there is no risk of disease development. In 2009 a new qPCR diagnostic assay was developed by Barnes et al. to eliminate false positive results. Both qPCR assays were tested against other rust pathogens; however, neither of these assays was tested against closely related Phakopsora spp. (other than P. meibomiae) that are known to occur in the continental United States. The species that we will test include P. arthuriana (collected from Puerto Rico), P. crotonis (collected from Florida), P. meibomiae (collected from Costa Rica, Puerto Rico, and Panama), P. nishidana (collected from Puerto Rico), P. pachyrhizi (collected from USA and Zimbabwe), P. tecta (collected from South Africa), and an unknown Phakopsora species (collected from Ecuador). All of these species, except for P. arthuriana, which was reported in Latin America and Puerto Rico, are found primarily in the southern United States, with the exception of P. crotonis, which also was reported in Indiana and Illinois. Phakopsora crotonis and P. tecta are closely related to P. pachyrhizi and P. meibomiae as determined by molecular phylogenetic analysis. We will assess the two diagnostic assays against these Phakopsora spp.