Induced variability in homozygous and heterozygous genotypes of tobacco

Dry seeds of homozygous pure breeding lines of chewing tobacco (Nicotiana tabacum L.), Sona, bandi and their F₁ hybrid were treated with chemical mutagen EMS at three concentrations (0.1, 0.3 and 0.5%) for 12 h. In M₁ generation, based on seed germination and seedling growth, homozygous material was found to be more sensitive than heterozygous material. Complete seed mortality was observed following treatment with 0.5% EMS. In M₂ generation, range widened for all characters in different populations. Mean values increased in F₂ over midparent but was significantly lowered in M₂ and F₂ M₂ for all the characters except total cured leaf yield. There was no significant difference in mean leaf thickness which marginally decreased in F₂ and increased in M₂ and F₂ M₂. Significant increase in nicotine content was observed in F₁ and M₂ but in F₂ M₂ it decreased significantly. A significant increase in variation was evident in F₂ and M₂ for all characters but in F₂ M₂ it was so for leaf breadth and first grade leaf yield. The magnitude of the induced variation was in order of M₂ < F₂ < F₂ M₂. Variations from hybridization and mutation were generally not cumulative.