Pedigree and Breeding Methods
Delgold was developed in an inter-specific hybridization study. A colchicine-derived tetraploid (4n) Nicotiana tabacum L. 'Virginia 115' was crossed in 1971 to a deploid(2n) female parent from N. rustica L. 'Ba-bor'. The resultant interspecific hybrid did not produce seed on selfing indicating sterility. However, repeated pollination of the highly sterile F, inter-specific hybrid with diploid (2n) Virginia 115 produced a few backcross-one (BC,) seed in 1972. These BC, progenies were grown in a breeding nursery in 1973 for their agronomic, morphological and chemical characterization. Most of the BC, progenies were off-types Can. J. Plant Sci. 64t 233-236 (Jan. 1984) 233 with a bushy habit of growth and high degree of sterility. An individual BC' selectant, with high leaf total alkaloids, was backcrossed to N. tobaco 'Hicks Broad-leaf' as a diploid female parent in the greenhouse. A selected high leaf total alkaloid genotype from the second backcross (BCr) generation was further back ordered as the female parent with a diploid Virginia 115. Normal floral fertility and flue-cured tobacco phenotype were restored among the segregants of the BC, generation. Subsequent to the BC. generation, individual plant selection and selfing were carried out, and by 1976 a fully fertile diploid strain 76N2 was evaluated in an early generation testing program. A set of seven well-differentiated sister-lines, based on leaf dimension and shape, plant type and color, was established from the 76N2 bulk population. Performance evaluations conducted under the designation 76N2-E identified the strain to be superior to its other sister-lines and the check cultivar Virginia115. Certified seed production began in 1980.