Population Improvement by Mass Selection in the Early Maturing Cultivars of Motihari Tobacco (N. rustica L.) in North Bengal

摘要

Mass selection was carried out for three successive crop seasons for desirable traits like uniformity, true to the type with desired phenotype in the heterogeneous populations of prevalent local cultivars/land races of early maturing Motihari tobacco (N. rustica L.) commonly known as Bitri type namely Manda, Tangua Manda, Bombai and Bitri. Mass selection upgraded means of all the four populations over first year for all the characters except cured leaf yield and the magnitude of increase for different characters ranged from 1.23 to 30.24%. Extent of genotypic variation relative to environmental variation was lower for yield and quality characters leading to low heritability. In contrast to higher magnitude of genotypic coefficient of variability and heritability observed in the populations in first generation, it gradually declined in the successive generations. As a result of mass selection over three generations, stability was observed in terms of rise in homozygosity. Estimates of genetic variance in the populations for different characters were significant in 50 out of 84 cases, however, the number of significant cases decreased with each cycle of mass selection. Continuation of mass selection for few more cycles is expected to increase the desirable improvement in yield and quality.