Agronomic Performance and Nature of Gene Effects in Progenitor Species‐Derived Genotypes of Tobacco1

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Abstract
An investigation was conducted to determine the nature of genetic effects in segregating populations produced by crossing selected progenitor species‐derived tobacco (Nicotiana tabacum L.) lines to the tobacco cultivar used in the original interspecific hybridization.Two genetically stable tobacco lines developed from interspecific crosses of N. tabacum ✕ N. sylvestris Speg. and Comes and N. tabacum ✕ N. otophora Griesbach, respectively, were crossed with the flue‐cured tobacco cultivar, ‘SC 58’, and F2 and backcross generations were produced. Data on agronomic characters and chemical constituents of cured leaf were collected and subjected to generation means analyses.The tobacco parent exhibited poorer performance than other generations for all agronomic characters, except grade index and chemical attributes of cured leaves. Conversely, species‐derived lines were frequently higher performing for yielding ability, days to flower, plant height, and number of leaves per plant, but cured leaf quality was inferior to other genetic entries. Significant positive heterosis for yield was found in three of the four families, and inbreeding depression was usually low.Additive genetic effects were significant for all characters in all families. Yield had significant dominance effects for every family while other chacacters varied from family to family. Frgm an evolutionary aspect of gene action, species germplasm tended to exhibit dominance in a positive direction for yield, days to flower, plant height, and number of leaves per plant, and in a negative direction for leaf quality. Deviations from the additive and dominance model were not observed.