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Title: A real-time PCR assay for the differentiation of Pantoea stewartii subsp. stewartii from Pantoea stewartii subsp. indologenes in corn seed

Author
item Pal, Narinder
item BLOCK, CHARLES - Iowa State University

Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2017
Publication Date: 12/1/2017
Citation: Pal, N., Block, C.C. 2017. A real-time PCR assay for the differentiation of Pantoea stewartii subsp. stewartii from Pantoea stewartii subsp. indologenes in corn seed [abstract]. American Phytopathological Society Abstracts. 107(12S):S5.52. https://doi.org/10.1094/PHYTO-107-12-S5.1.
DOI: https://doi.org/10.1094/PHYTO-107-12-S5.1

Interpretive Summary:

Technical Abstract: Stewart's wilt of corn caused by the bacterium Pantoea stewartii subsp. stewartii is a seedborne disease of major phytosanitary importance. Over 60 countries have restrictions on seed imports to prevent introduction of the pathogen. Traditional methods for detection of P. stewartii include field inspection of parent plants and an ELISA seed assay. Current lab methods (ELISA and PCR) cannot readily distinguish P. stewartii subsp. stewartii from the closely-related but non-pathogenic (on corn) subspecies P. stewartii subsp. indologenes. We developed a SYBR-Green based real-time PCR assay targeting the intergenic region of the cps gene cluster for the specific detection of P. stewartii subsp. stewartii. The assay detected all 27 P. stewartii subsp. stewartii reference strains while 13 Pantoea agglomerans, 11 P. ananatis, seven P. stewartii subsp. indologenes, and four distantly-related Erwinia species were negative. The detection limits for purified genomic DNA and cells were 0.1 pg and 11 CFU per PCR reaction, respectively. The assay successfully detected P. stewartii subsp. stewartii from 16 naturally-infected seed lots. Several seed lots that had tested positive by ELISA and published PCR methods were negative for P. stewartii subsp. stewartii and were confirmed by sequencing to be subspecies indologenes. By distinguishing the two subspecies, the assay may help prevent unnecessary restrictions on the international movement of corn seed.