@article{lewis_rose_2011, title={Identification of Tobacco Haploids on the Basis of Transgenic Overexpression of PAP1 from Arabidopsis thaliana}, volume={51}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2010.09.0546}, abstractNote={Haploid plants have utility in plant breeding for several purposes. In tobacco (Nicotiana tabacum L.) gynogenic haploids can be produced from seed due to parthenogenesis. For practical use, a system is needed to identify infrequent haploid plants at the seed or seedling stage. Interspecific hybridization with N. africana is presently used to isolate gynogenic tobacco haploids because a suitable dominant seedling marker does not currently exist for N. tabacum. Here we investigated the utility of a purple seedling trait conferred by overexpression of the Arabidopsis gene, PAP1, to identify gynogenic haploids produced from seed. Two tobacco cultivars were crossed as females with a genetic stock homozygous at two 35S:PAP1 transgene loci. Gynogenic haploids were recognized as green seedlings among purple F 1 hybrid seedlings. The average frequency of gynogenic haploidy using this system was f = 0.00027. For comparison, the same cultivars were also hybridized as females with N. africana. The average frequency of gynogenic haploidy using this system was approximately seven times higher than that observed for the 35S:PAP1 system. Having a dominant seedling marker for N. tabacum may permit development of genetic stocks that contribute to an increased predisposition for haploid formation via parthenogenesis. In addition, the 35S:PAP1 genetic marker may have utility for identifying androgenic haploids from seed for the purpose of rapidly generating alloplasmic lines of tobacco.}, number={4}, journal={CROP SCIENCE}, author={Lewis, Ramsey S. and Rose, Cara}, year={2011}, month={Jul}, pages={1491–1497} }
 @article{lewis_rose_2010, title={Agronomic Performance of Tobacco Mosaic Virus-Resistant Tobacco Lines and Hybrids Possessing the Resistance Gene N Introgressed on Different Chromosomes}, volume={50}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci2009.10.0615}, abstractNote={Resistance to tobacco mosaic virus (TMV) is conferred by the single dominant gene, N, in Nicotiana glutinosa L. This gene has been transferred to cultivated tobacco (N. tabacum L.) via interspecific hybridization and backcrossing. Current TMV-resistant (TMV R ) cultivars carry N introgressed on chromosome H of the N. tabacum genome. Undesirable linkage drag effects have caused associations with reduced yields and/or quality in flue-cured tobacco, however. Other germplasm lines possess the gene transferred onto an alternative chromosome. The objective of this research was to compare the agronomic performance of nearly isogenic lines (NILs) and hybrids possessing N on different chromosomes and originating from four N donor lines. Regardless of the source of the gene, Nn heterozygotes were intermediate in value for yield, cash return, and cured leaf chemistry relative to nn and NN homozygotes. Lines and hybrids carrying N transferred from Xanthi nc produced the highest yields, whereas those possessing N introduced from TI 1473 exhibited the lowest yields. Overall, materials possessing N on chromosome H were not found to be significantly different for yield, grade index, value per hundred weight (US$ cwt -1 ), or cash return from those carrying the resistance gene on the alternative chromosome. Breeding strategies designed to reduce the amount of N. glutinosa chromatin linked to N are needed to develop TMV R flue-cured tobacco cultivars that do not exhibit an accompanying yield penalty.}, number={4}, journal={CROP SCIENCE}, author={Lewis, Ramsey S. and Rose, Cara}, year={2010}, pages={1339–1347} }