@article{shi_jin_nifong_shew_lewis_2021, title={Homoeologous chromosome exchange explains the creation of a QTL affecting soil-borne pathogen resistance in tobacco}, ISSN={["1467-7652"]}, DOI={10.1111/pbi.13693}, abstractNote={Summary}, journal={PLANT BIOTECHNOLOGY JOURNAL}, author={Shi, Rui and Jin, Jing and Nifong, Jessica M. and Shew, David and Lewis, Ramsey S.}, year={2021}, month={Oct} }
 @article{ma_heim_humphry_nifong_lewis_2020, title={Characterization of Phn15.1, a Newly Identified Phytophthora nicotianae Resistance QTL in Nicotiana tabacum}, volume={104}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-10-19-2257-RE}, abstractNote={ Phytophthora nicotianae is an oomycete that causes black shank, one of the most economically important diseases affecting tobacco production worldwide. Identification and introgression of novel genetic variability affecting partial genetic resistance to this pathogen is important because of the increased durability of partial resistance over time as compared with genes conferring immunity. A previous mapping study identified a quantitative trait locus (QTL), hereafter designated as Phn15.1, with a major effect on P. nicotianae resistance in tobacco. In this research, we describe significantly improved resistance of nearly isogenic lines (NILs) of flue-cured tobacco carrying the introgressed Phn15.1 region derived from highly resistant cigar tobacco cultivar Beinhart 1000. The Phn15.1 region appeared to act in an additive or partially dominant manner to positively affect resistance. To more finely resolve the position of the gene or genes underlying the Phn15.1 effect, the QTL was mapped with an increased number of molecular markers (single-nucleotide polymorphisms) identified to reside within the region. Development and evaluation of subNILs containing varying amounts of Beinhart 1000-derived Phn15.1-associated genetic material permitted the localization of the QTL to a genetic interval of approximately 2.7 centimorgans. Importantly, we were able to disassociate the Beinhart 1000 Phn15.1 resistance alleles from a functional NtCPS2 allele(s) which contributes to the accumulation of a diterpene leaf surface exudate considered undesirable for flue-cured and burley tobacco. Information from this research should be of value for marker-assisted introgression of Beinhart 1000-derived partial black shank resistance into flue-cured and burley tobacco breeding programs. }, number={6}, journal={PLANT DISEASE}, author={Ma, Justin M. and Heim, Crystal B. and Humphry, Matt and Nifong, Jessica M. and Lewis, Ramsey S.}, year={2020}, month={Jun}, pages={1638–1646} }
 @article{ma_hancock_nifong_kernodle_lewis_2020, title={Identification and editing of a hybrid lethality gene expands the range of interspecific hybridization potential in Nicotiana}, volume={133}, ISSN={["1432-2242"]}, DOI={10.1007/s00122-020-03641-w}, abstractNote={Identification and inactivation of hybrid lethality genes can be used to expand the available gene pool for improvement of a cultivated crop species. Hybrid lethality is one genetic mechanism that contributes to reproductive isolation in plants and serves as a barrier to use of diverse germplasm for improvement of cultivated species. A classic example is the seedling lethality exhibited by progeny from the Nicotiana tabacum × N. africana interspecific cross. In order to increase the body of knowledge on mechanisms of hybrid lethality in plants, and to potentially develop tools to circumvent them, we utilized a transposon tagging strategy to identify a candidate gene involved in the control of this reaction. N. tabacum gene Nt6549g30 was identified to code for a class of coiled-coil nucleotide-binding site-leucine-rich repeat (CC-NBS-LRR) proteins, the largest class of plant defense proteins. Gene editing, along with other experiments, was used to verify that Nt6549g30 is the gene at the N. tabacum Hybrid Lethality 1 (NtHL1) locus controlling the hybrid lethality reaction in crosses with N. africana. Gene editing of Nt6549g30 was also used to reverse interspecific seedling lethality in crosses between N. tabacum and eight of nine additional tested species from section Suaveolentes. Results further implicate the role of disease resistance-like genes in the evolution of plant species and demonstrate the possibility of expanding the gene pool for a crop species through gene editing.}, number={10}, journal={THEORETICAL AND APPLIED GENETICS}, author={Ma, Justin and Hancock, Wesley G. and Nifong, Jessica M. and Kernodle, Sheri P. and Lewis, Ramsey S.}, year={2020}, month={Oct}, pages={2915–2925} }
 @article{zeng_nifong_liu_huang_fang_lewis_li_2019, title={Evaluating diverse systems of tobacco genetic resistance to Phytophthora nicotianae in Yunnan, China}, volume={68}, ISSN={["1365-3059"]}, DOI={10.1111/ppa.13091}, abstractNote={Black shank, caused by the soilborne pathogen Phytophthora nicotianae, is one of the most devastating diseases affecting tobacco production in China. The most effective strategy for reducing economic loss from this pathogen is development and use of resistant tobacco varieties. Multiple sources and systems of resistance have been developed in the Western Hemisphere; however, populations of P. nicotianae are variable around the world, including the predominance of different races. Different P. nicotianae isolates may react differently on tobacco plants with different systems of resistance, a possibility that could complicate the breeding of cultivars with resistance that is effective in different tobacco production regions worldwide. The objective of this research was to evaluate an array of tobacco germplasm possessing different systems of genetic resistance to black shank disease in tobacco‐growing regions of Yunnan, China. Resistance types included simply inherited resistance mechanisms introgressed from wild Nicotiana relatives and polygenic partial resistance systems of N. tabacum origin. The loci of Wz exhibited high level resistance to black shank in the five diverse disease environments in Yunnan, China. K326 Php/−Wz/− genotype and Beinhart 1000 exhibited the greatest levels of resistance in both 2015 and 2016. Field observed results for 13 tobacco genotypes were highly correlated with those tested in growth chamber evaluation. These findings suggest that both Wz− and Beinhart 1000‐mediated resistance have important commercial value in flue‐cured tobacco breeding programmes in China. Cultivars developed for black shank resistance in China may also have utility in other tobacco‐growing areas.}, number={9}, journal={PLANT PATHOLOGY}, author={Zeng, J. M. and Nifong, J. and Liu, Y. and Huang, C. J. and Fang, D. H. and Lewis, R. S. and Li, Y. P.}, year={2019}, month={Dec}, pages={1616–1623} }
 @article{ma_heim_humphry_nifong_lewis_2019, title={Genetic analysis of Phn7.1, a major QTL conferring partial resistance to Phytophthora nicotianae in Nicotiana tabacum}, volume={39}, DOI={10.1007/s11032-018-0923-x}, number={1}, journal={MOLECULAR BREEDING}, author={Ma, Justin M. and Heim, Crystal and Humphry, Matt and Nifong, J. M. and Lewis, Ramsey S.}, year={2019} }