@article{nifong_nicholson_shew_lewis_2011, title={Variability for Resistance to Phytophthora nicotianae Within a Collection of Nicotiana rustica Accessions}, volume={95}, ISSN={["1943-7692"]}, DOI={10.1094/pdis-11-10-0862}, abstractNote={Black shank, caused by Phytophthora nicotianae, is one of the most important diseases affecting tobacco (Nicotiana tabacum) production worldwide. Many current tobacco cultivars possess immunity to race 0 of this pathogen conferred by introgressed dominant genetic factors. Novel alleles conditioning resistance to alternative races are desired. The objective of this research was to evaluate variability for black shank resistance within a collection of N. rustica germplasm using both soilborne disease nurseries and controlled race-specific (race 0 and race 1) inoculations. Nearly all of the 86 accessions studied exhibited very high resistance to race 0, and many displayed levels of race 1 resistance greater than that exhibited by the resistant flue-cured tobacco check, ‘K 346’. Materials found to be highly resistant to race 0 and race 1 in growth-chamber experiments also had the best survivability in field disease nurseries. N. rustica accessions TR 6, TR 12, TR 16, TR 21, TR 20, TR 48, TR 54, TR 57, and TR 69 could be sources of novel alleles with large effects on black shank resistance, and could have value for burley and flue-cured tobacco breeding.}, number={11}, journal={PLANT DISEASE}, author={Nifong, J. M. and Nicholson, J. S. and Shew, H. D. and Lewis, R. S.}, year={2011}, month={Nov}, pages={1443–1447} }
 @article{moon_nifong_nicholson_heineman_lion_hoeven_hayes_lewis_2009, title={Microsatellite-based Analysis of Tobacco (Nicotiana tabacum L.) Genetic Resources}, volume={49}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2009.01.0024}, abstractNote={Little is currently known about the genetic variation within diverse gene pools of cultivated tobacco (Nicotiana tabacum L.). Knowledge in this area could aid in future germplasm maintenance activities, provide additional information in the area of N. tabacum population genetics, and assist in selection of materials for breeding or genetic investigations. To this end, 702 N. tabacum accessions from the U.S. Nicotiana Germplasm Collection were genotyped with 70 microsatellite markers. A total of 1031 alleles were detected, with an average of 14.7 alleles per marker. Average gene diversity was quite large (0.7362) and was three times the value for a diverse population of U.S. fl ue-cured tobacco. Cluster analysis using various distance coeffi cients generated seven consistent groups. Patterns of geographic-specifi c clustering were frequent but not universal. An analysis of molecular variance for tobacco collected from Central and South America revealed that 92% of the total genetic variation among samples could be attributed to country-specifi c subpopulations. There was also a signifi cant level of population subdivision between country-specifi c subpopulations, however. Tobacco samples collected from Peru had both the largest average gene diversity and the largest mean genetic distance, although N. tabacum collected from Mexico had the greatest allelic richness. Tobacco samples collected from Argentina were the most divergent subpopulation.}, number={6}, journal={CROP SCIENCE}, author={Moon, H. S. and Nifong, J. M. and Nicholson, J. S. and Heineman, A. and Lion, K. and Hoeven, R. and Hayes, A. J. and Lewis, R. S.}, year={2009}, pages={2149–2159} }