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.