@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{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} }