Success of efforts for improvement of the crop depends upon the magnitude of the genetic variability and extent to which the desirable characters are heritable

Success of efforts for improvement of the crop depends upon the magnitude of the genetic variability and extent to which the desirable characters are heritable. Variation among the individuals of a population due to their genetic constitution is important for varietal adaptability and effective selection. The biological variation consists of (1) Phenotypic (2) Genotypic and (3) Environmental components. The phenotypic variability consists of genetic and environmental variation and is observable. The genetic variability is the inherent variation which consists of additive, dominance and epistatic components.
Following are reviews available on genetic variability .However only few of them reviewed here.
Deokar et al. (1985) studied wide range of variability for plant height seed yield per plant in safflower, number of capitula per plant,. The genotypic coefficient of variation was ranged between 34 per cent for hull content and 29.39 per cent for seed yield per plant.
Mane et al. (1999) observed that a closed similarity between the corresponding estimated of PCV and GCV suggestion that the environment have little role in the expressions of different characters. High PCV were recorded for number of seed/capsule for number of secondary branch under irrigated environment, where as it was highest in number of secondary branches following number of sees/capsular under rain fed conditions.
Seta et al. (1999) studied that in vitro pollen (s) can also be used as alternate source in creations genetic variability which can be utilize in breeding program aimed at the enhancement of certain agronomic traits such as seed yield and oil content.
Banerjee and Chaudhary (1999) observed high genotypic and phenotypic variation in number of capitula per plant and plant height seed yield per plant. High phenotypic coefficient of variation and genotypic coefficient of variation values were observed for number of capitula per plant and plant height.