Genetic Variability

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Starting with The Name of Allah Almighty

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Topics

• Genetic Variability
• Basis of Plant Breeding
• Components of Variability
• Estimation of Heritability

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Genetic Variability

• It is a measure of the tendency of individual
  genotypes in a population to vary from one
  another.

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Importance

• Variability is an important factor in evolution
  as it affects an individual's response to
  environmental stress and thus can lead to
  differential survival of organisms within a
  population due to natural selection of the fit
  variants.

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Causes of Variabiity

• Homologous recombination
• Immigration, emigration, and translocation
• Polyploidy
• Diffuse centromeres
• Genetic mutations

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Basis of Plant Breeding

• Plant breeding
• is the art and science of changing the traits of
  plants in order to produce desired
  characteristics.

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History

• Plant breeding started with sedentary agriculture
  and particularly the domestication of the first
  agricultural plants, estimated about 9,000 to
  11,000 years ago.

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Objectives of Plant Breeding

• Traits that breeders have tried to incorporate
  into crop plants in the last 100 years include
• 1. Increased quality and yield of the crop
• 2. Increased tolerance of environmental
  pressures (salinity, extreme temperature,
  drought)
• 3. Resistance to viruses, fungi and bacteria
• 4. Increased tolerance to insect pests
• 5. Increased tolerance of herbicides.

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Steps of plant breeding

• The following are the major activities of plant
  breeding
• 1. Collection of variation
• 2. Selection
• 3. Evaluation
• 4. release
• 5. Multiplication
• 6. Distribution of the new variety

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Components of Variability,

• Marker assisted selection
• Reverse breeding and doubled haploids (DH)
• Genetic modification

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Estimation of Heritability

• Heritability It is the relation of genotypic
  variance to total phenotypic variance, which
  includes both genetic and environmental variance.
• Or
• The inherited portion of the variability is known
  as Heritability.

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Estimation methods

• Broad sense Heritability
• It refers to the ratio of genetic variance to the
  Phenotypic variance with a population.
• BSHVg/ Vp
• Where Vg Genetic Variance
• VpPhenotypic Variance
• While
• VpVgVe
• Where
• VeEnvironmental Variance

• Narrow sense Heritability
• It is the ratio of additive genetic variance to
  the total variance with in a population.
• NSHV a / Vp
• Where
• Va Additive genetic variance
• VpPhenotypic variance.

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The End

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• A presentation By
• M.Shahid Saeed
• 5th term (P.B.G)
• Roll No. 599
• Bsc(Hons.) Agriculture
• Faculty of Agriculture
• Gomal University,D.I.Khan.