Charles S. Johnson, Professor, Jeremy A. Pattison, Assistant Professor, and Elizabeth M. Clevinger, Research Specialist Senior, Southern Piedmont Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Blackstone 23824; Thomas A. Melton, Assistant Director and Associate State Program Leader ANR/CRD, North Carolina Cooperative Extension, North Carolina State University, Raleigh 27695; Bruce A. Fortnum,Professor, Clemson University, Pee Dee Research and Education Center, Florence, SC 29506; and Asamina Mila, Assistant Professor and Extension Specialist, Department of Plant Pathology, North Carolina State University, Raleigh 27695
Corresponding author: Charles S. Johnson. firstname.lastname@example.org
Johnson, C. S., Pattison, J. A., Clevinger, E. M., Melton, T. A., Fortnum, B. A., and Mila, A. 2008. Clarifying the source of black shank resistance in flue-cured tobacco. Online. Plant Health Progress doi:10.1094/PHP-2008-0618-02-RS.
Widespread use of resistance to race 0 of Phytophthora nicotianae in flue-cured tobacco (Nicotiana tabacum) has increased problems with race 1 in commercial fields. The RAPD marker UBC30, tightly linked to the Ph gene for resistance to race 0, was used to clarify the presence of the Ph gene in specific cultivars to enable farmers to more appropriately match cultivar resistance to the pathogen races predominating in their fields. The marker UBC30 was present in 20 of the 31 flue-cured tobacco cultivars tested, including CC 27, GL 350, NC 196, SP 220, SP 225, SP 227, and NC 810. These cultivars were previously thought to not possess the Ph gene. Presence of UBC30 was highly correlated (r = 0.93;P ≤ 0.001) with survival in fields infested primarily with race 0, and with greater survival in fields infested primarily with race 0 versus race 1 of the pathogen (r = 0.76; P ≤ 0.001). The likely presence of the Ph gene in so many currently grown flue-cured tobacco cultivars may limit farmers’ ability to shift pathogen populations back to race 0 from race 1 via the recommended cultivar rotation strategy.