@article{johnson_wernsman_lamondia_2009, title={Effect of a Chromosome Segment Marked by the Ph-p Gene for Resistance to Phytophthora nicotianae on Reproduction of Tobacco Cyst Nematodes}, volume={93}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS-93-3-0309}, abstractNote={ Host resistance is an important strategy for managing Globodera tabacum subsp. solanacearum and G. tabacum subsp. tabacum, important nematode pests of flue-cured tobacco (Nicotiana tabacum) in Virginia, and cigar wrapper tobacco (N. tabacum) in Connecticut and Massachusetts, respectively. Field research from 1992 to 2005 evaluated reproduction of G. tabacum subsp. solanacearum on genotypes with and without a chromosome segment from N. plumbaginifolia containing a gene (Php) that conferred resistance to race 0 of Phytophthora nicotianae (causal agent of tobacco black shank). Ratios of G. tabacum subsp. solanacearum eggs/500 cm3 soil at the end versus the beginning of experiments (Pf/Pi) were significantly lower in cultivars and breeding lines possessing the Php-containing chromosome segment from N. plumbaginifolia compared with genotypes without the segment. Numbers of vermiform G. tabacum subsp. solanacearum juveniles in roots were similar among genotypes but numbers of swollen and pyriform nematodes were significantly lower for the known G. tabacum subsp. solanacearum resistant cv. NC 567 and in genotypes possessing the Php gene compared with genotypes and cultivars without the gene. In a 2003 greenhouse test, the percentage of plants with visible G. tabacum subsp. tabacum cysts was also significantly lower for parental and progeny genotypes homozygous and heterozygous, respectively, for Php compared with similar lines without the gene. These results indicate a close linkage or association between a likely single, dominant gene (Php) for resistance to P. nicotianae and suppressed reproduction by G. tabacum subsp. solanacearum and G. tabacum subsp. tabacum. Further research to accurately elucidate the relationships among these genes could lead to significant improvements in tobacco disease control. }, number={3}, journal={PLANT DISEASE}, author={Johnson, C. S. and Wernsman, E. A. and LaMondia, J. A.}, year={2009}, month={Mar}, pages={309–315} }
 @article{lewis_linger_wolff_wernsman_2007, title={The negative influence of N-mediated TMV resistance on yield in tobacco: linkage drag versus pleiotropy}, volume={115}, ISSN={["0040-5752"]}, DOI={10.1007/s00122-007-0552-y}, abstractNote={Resistance to tobacco mosaic virus (TMV) is controlled by the single dominant gene N in Nicotiana glutinosa L. This gene has been transferred to cultivated tobacco (N. tabacum L.) by interspecific hybridization and backcrossing, but has historically been associated with reduced yields and/or quality in flue-cured tobacco breeding materials. Past researchers have suggested the role of pleiotropy and/or linkage drag effects in this unfavorable relationship. Introduction of the cloned N gene into a TMV-susceptible tobacco genotype (cultivar 'K326') via plant transformation permitted investigation of the relative importance of these possibilities. On average, yield and cash return ($ ha(-1)) of 14 transgenic NN lines of K326 were significantly higher relative to an isoline of K326 carrying N introduced via interspecific hybridization and backcrossing. The negative effects of tissue culture-induced genetic variation confounded comparisons with the TMV-susceptible cultivar, K326, however. Backcrossing the original transgenic lines to non-tissue cultured K326 removed many of these unfavorable effects, and significantly improved their performance for yield and cash return. Comparisons of the 14 corresponding transgenic NN backcross-derived lines with K326 indicated that linkage drag is the main factor contributing to reduced yields in TMV-resistant flue-cured tobacco germplasm. On average, these transgenic lines outyielded the conventionally-developed TMV-resistant K326 isoline by 427 kg ha(-1) (P < 0.05) and generated $1,365 ha(-1) more (P < 0.05). Although transgenic tobacco cultivars are currently not commercially acceptable, breeding strategies designed to reduce the amount of N. glutinosa chromatin linked to N may increase the likelihood of developing high-yielding TMV-resistant flue-cured tobacco cultivars.}, number={2}, journal={THEORETICAL AND APPLIED GENETICS}, author={Lewis, R. S. and Linger, L. R. and Wolff, M. F. and Wernsman, E. A.}, year={2007}, month={Jul}, pages={169–178} }
 @article{liu_levin_murray_wernsman_weissinger_2003, title={A multi-generation analysis of the stability of transgenic virus resistance in doubled-haploid tobacco lines}, volume={12}, number={2}, journal={Molecular Breeding}, author={Liu, Y. S. and Levin, J. S. and Murray, J. S. and Wernsman, E. A. and Weissinger, A. K.}, year={2003}, pages={145–156} }
 @article{johnson_wolff_wernsman_rufty_2002, title={Marker-assisted selection for resistance to black shank disease in tobacco}, volume={86}, ISSN={["1943-7692"]}, DOI={10.1094/PDIS.2002.86.12.1303}, abstractNote={ Bulked segregant (BSA) and random amplified polymorphic DNA (RAPD) analyses were used to identify markers linked to the dominant black shank resistance gene, Ph, from flue-cured tobacco (Nicotiana tabacum) cv. Coker 371-Gold. Sixty RAPD markers, 54 in coupling and 6 in repulsion phase linkage to Ph, were identified in a K 326-derived BC1F1 (K 326-BC1F1) doubled haploid (DH) population. Thirty RAPD markers, 26 in coupling and 4 in repulsion phase linkage to Ph, were used to screen 149 K 326-BC2F1 haploid plants. Complete linkage between the 26 coupling phase markers and Ph was confirmed by screening 149 K 326-BC2F1 DH lines produced from the haploid plants in black shank nurseries. RAPD markers OPZ-5770 in coupling and OPZ-7370 in repulsion phase linkage were used to select plants homozygous for the Ph gene for further backcrossing to the widely grown flue-cured cultivar K 326. Black shank disease nursery evaluation of 11 K 326-BC4S1 lines and their testcross hybrids to a susceptible tester confirmed linkage between Ph and OPZ-5770. The results demonstrated the efficiency of marker-assisted selection for Ph using a RAPD marker linked in coupling and repulsion. Complete linkage between 26 RAPD markers and the Ph gene was confirmed in the K 326-BC5 generation, and RAPD phenotypes were stable across generations and ploidy levels. These RAPD markers are useful in marker-assisted selection for Ph, an important black shank resistance gene in tobacco. }, number={12}, journal={PLANT DISEASE}, author={Johnson, ES and Wolff, MF and Wernsman, EA and Rufty, RC}, year={2002}, month={Dec}, pages={1303–1309} }
 @article{johnson_wolff_wernsman_atchely_shew_2002, title={Origin of the black shank resistance gene, Ph, in tobacco cultivar Coker 371-gold}, volume={86}, ISSN={["0191-2917"]}, DOI={10.1094/PDIS.2002.86.10.1080}, abstractNote={ Flue-cured tobacco (Nicotiana tabacum) cultivar Coker 371-Gold (C 371-G) possesses a dominant gene, Ph, that confers high resistance to black shank disease, caused by race 0 of the soil-borne pathogen Phytophthora parasitica var. nicotianae. The origin of this gene is unknown. Breeding lines homozygous for the Ph gene were hybridized with NC 1071 and L8, flue-cured and burley genotypes known to possess qualitative resistance genes from Nicotiana plumbaginifolia and N. longiflora, respectively. The F1 hybrids were out-crossed to susceptible testers and the progenies evaluated in field black shank nurseries and in greenhouse disease tests with P. parasitica var. nicotianae race 0. Results showed that Ph was allelic to Php from N. plumbaginifolia in NC 1071. Testcross populations of hybrids between burley lines homozygous for Ph and L8, possessing Phl from N. longiflora, showed that Ph and Phl integrated into the same tobacco chromosome during interspecific transfer. Nevertheless, the two loci were estimated to be 3 cM apart. Random amplified polymorphic DNA (RAPD) analyses of the testcross progenies confirmed that recombination between the two loci was occurring. Forty-eight RAPD markers linked to Ph in doubled haploid lines were used in cluster analyses with multiple accessions of N. longiflora and N. plumbaginifolia, breeding lines L8, NC 1071, and DH92-2770-40, and cultivars K 326, Hicks, and C 371-G. A cladogram or region tree confirmed the data obtained from field and greenhouse trials, that Ph, transferred from C 371-G to DH92-2770-40, and Php in NC 1071 were allelic and originated from N. plumbaginifolia. }, number={10}, journal={PLANT DISEASE}, author={Johnson, ES and Wolff, MF and Wernsman, EA and Atchely, WR and Shew, HD}, year={2002}, month={Oct}, pages={1080–1084} }
 @article{lewis_wernsman_2001, title={Efforts to initiate construction of a disease resistance package on a designer chromosome in tobacco}, volume={41}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci2001.4151420x}, abstractNote={Gene cloning and transformation can be used to circumvent linkage drag effects that can plague conventional interspecific gene transfers. These techniques can also be used to create desirable genetic linkages. Use of Nicotiana glutinosa L. N‐gene mediated TMV (tobacco mosaic virus) resistance in flue‐cured tobacco, N tabacum L., has been limited due to linkage drag effects. Transformation was used to introduce the cloned N‐gene into NC152, a chromosome addition line possessing a chromosome pair from N africana. This chromosome has been proposed to be used as a “designer chromosome” into which numerous transgenes could be inserted to form a desirable linkage package. The system could be used to shuttle a large number of transgenes from genotype to genotype. One hundred thirty‐six primary transformants possessing the N transgene were produced and hybridized with TMV‐susceptible ‘Petite Havana.’ These may serve as valuable TMV‐resistant breeding materials. For each independent transformant, BC1F1 families which segregated for TMV resistance and the addition chromosome were generated. Data from cosegregation, transmission, and molecular analyses were used to conclude that one transformant possessed an insertion of the N‐gene in the addition chromosome. By inserting N in the chromosome, we initiated construction of a disease resistance package by linking the TMV resistance gene with a potyvirus resistance gene(s) native to the chromosome. Occasional loss of the transgene, however, may be evidence of previously undetected interchromosomal recombination, and may have implications for use of this system in cultivar development.}, number={5}, journal={CROP SCIENCE}, author={Lewis, RS and Wernsman, EA}, year={2001}, pages={1420–1427} }
 @article{fitzmaurice_nguyen_wernsman_thompson_conkling_1999, title={Transposon tagging of the sulfur gene of tobacco using engineered maize Ac/Ds elements}, volume={153}, number={4}, journal={Genetics}, author={Fitzmaurice, W. P. and Nguyen, L. V. and Wernsman, E. A. and Thompson, W. F. and Conkling, M. A.}, year={1999}, pages={1919–1928} }
 @article{yi_rufty_wernsman_conkling_1998, title={Mapping the root-knot nematode resistance gene (Rk) in tobacco with RAPD markers}, volume={82}, ISSN={["0191-2917"]}, DOI={10.1094/PDIS.1998.82.12.1319}, abstractNote={ Random amplified polymorphic DNA (RAPD) analysis was conducted to map the Rk gene in tobacco which conditions resistance to races 1 and 3 of the root-knot nematode, Meloidogyne incognita. Resistant burley tobacco genotype NC 528, containing the Rk gene, and the susceptible cultivar Ky 14 were screened with 1,500 random decamers. A low rate of genetic polymor-phism (<10%) was detected among these lines. Two populations (F1 and F3) of maternally de-rived doubled haploid (MDH) lines of burley tobacco, developed from the cross NC 528 × Ky 14, were used to map the Rk gene. NC 528, Ky 14, three Rk-resistant (Rk-R) DNA bulks, andthree Rk-susceptible (Rk-S) bulks generated from F1-derived MDH individuals were screenedwith the primers that amplified bands polymorphic between Rk-R and Rk-S lines. A total of 67 F1MDH lines and 59 F3MDH lines were screened with the primers that amplified bands polymorphic between Rk-R bulks and Rk-S bulks to confirm linkage between candidate markers and the Rk gene. Sixteen RAPD markers were positioned at six loci in a map 24.1 centimorgans long. Six RAPD markers, including one identified in the F3MDH population, were mapped at the Rk locus. }, number={12}, journal={PLANT DISEASE}, author={Yi, HY and Rufty, RC and Wernsman, EA and Conkling, MC}, year={1998}, month={Dec}, pages={1319–1322} }
 @article{tanzer_thompson_law_wernsman_uknes_1997, title={Characterization of post transcriptionally suppressed transgene expression that confers resistance to tobacco etch virus infection in tobacco}, volume={9}, DOI={10.1105/tpc.9.8.1411}, abstractNote={Tobacco lines expressing transgenes that encode tobacco etch virus (TEV) coat protein (CP) mRNA with or without nonsense codons give rise to TEV-resistant tissues that have reduced levels of TEV CP mRNA while maintaining high levels of transgene transcriptional activity. Two phenotypes for virus resistance in the lines containing the transgene have been described: immune (no virus infection) and recovery (initial systemic symptoms followed by gradual recovery over several weeks). Here, we show that at early times in development, immune lines are susceptible to TEV infection and accumulate full-length CP mRNA. Therefore, immune lines also exhibit meiotic resetting, as is seen in the recovery lines, providing molecular evidence for a common mechanism of gene silencing and virus resistance in both cases. We also investigated the characteristics of two sets of low molecular weight RNAs that appear only in silenced tissue. One set has nearly intact 5[prime] ends, lacks poly(A) tails, and is associated with polyribosomes; the second set contains the 3[prime] end of the mRNA. Treating silenced leaf tissue with cycloheximide resulted in decreased levels of full-length mRNA and an increase in the levels of the low molecular weight RNAs, supporting a cytoplasmic decay mechanism that does not require ongoing translation. Surprisingly, mRNA from the transgene containing nonsense codons was associated with more ribosomes than expected, possibly resulting from translation from a start codon downstream of the introduced translational stop codons. We present a hypothesis for transgene/viral RNA degradation in which RNA degradation occurs in the cytoplasm while in association with polyribosomes.}, number={8}, journal={Plant Cell}, author={Tanzer, M. M. and Thompson, William and Law, M. D. and Wernsman, E. A. and Uknes, S.}, year={1997}, pages={1411–1423} }
 @article{carlson_wolff_shew_wernsman_1997, title={Inheritance of resistance to race 0 of Phytophthora parasitica var. nicotianae from the flue-cured tobacco cultivar Coker 371-Gold}, volume={81}, DOI={10.1094/PDIS.1997.81.11.1269}, abstractNote={ Black shank, caused by Phytophthora parasitica var. nicotianae, is a widespread and severe disease of tobacco throughout the southeastern United States. Partial resistance derived from the cigar tobacco cultivar Florida 301 has been the primary means of reducing losses to the disease for many years. The recently released tobacco cultivar, Coker 371-Gold (C 371-G), was found to provide an additional source of resistance to P. parasitica var. nicotianae. Although the resistance in C 371-G is being used widely by breeders, the origin and inheritance of this resistance mechanism was unknown. Two populations of doubled haploid lines derived from C 371-G were used to determine that C 371-G possesses a single, dominant gene designated Ph, which confers a very high level of resistance to race 0 of P. parasitica var. nicotianae. A greenhouse inoculation procedure was developed that provided an efficient means of screening for the presence of this resistance gene prior to selection in the field, and confirmed that Ph provides complete resistance to race 0 but no resistance to race 1 of P. parasitica var. nicotianae. Because Florida 301 resistance is effective against both races of the pathogen that occur in the major tobacco growing areas of the United States, combination of these two sources of resistance should provide enhanced protection of new tobacco cultivars to P. parasitica var. nicotianae. }, number={11}, journal={Plant Disease}, author={Carlson, S. R. and Wolff, M. F. and Shew, H. D. and Wernsman, E. A.}, year={1997}, pages={1269–1274} }
 @article{wernsman_1992, title={Sources of resistance to virus diseases}, number={3-4}, journal={Bulletin d'Information - CORESTA}, author={Wernsman, E. A.}, year={1992}, pages={113} }
 @article{wernsman_1992, title={Varied roles for the haploid sporophyte in plant improvement}, ISBN={0851987176}, journal={Plant breeding in the 1990s : proceedings of the Symposium on Plant Breeding in the 1990s}, publisher={Tucson, AZ : C.A.B. International}, author={Wernsman, E. A.}, editor={H.T. Stalker and Murphy, J.P.Editors}, year={1992}, pages={461} }
 @article{wernsman_1990, title={Germplasm sources and breeding strategies for developing tobaccos with disease and pest resistance}, number={7}, journal={Bulletin d'Information - CORESTA}, author={Wernsman, E. A.}, year={1990}, pages={55} }