Q7:

Briefly describe various steps involved in plant breeding.

Step 1: Collection of Variability

Genetic variability is the root of any breeding program. Breeders systematically collect and preserve all the diverse alleles of all genes in a given crop, known as the germplasm collection.

• Procedure: Exploration and collection of wild species, landraces, and cultivated varieties of the target crop.
• Significance: Provides the raw material for selection [Per Mendelian principles of genetic variation].

Step 2: Evaluation and Selection of Parents

The collected germplasm is evaluated to identify plants with desirable traits, such as high yield, disease resistance, or environmental adaptability.

• Process: Plants demonstrating the targeted traits are selected and multiplied to serve as parents in the breeding program.
• Requirement: Pure lines are created wherever possible by continuous self-pollination [By Law of Purity of Gametes].

Step 3: Cross-hybridization Among Selected Parents

This is the most critical step for creating genetic recombination. It involves cross-pollinating two plants with different desired traits.

Example: Crossing a high-yielding variety with a disease-resistant variety to produce a progeny possessing both traits.

• Emasculation: Removal of anthers from the female parent flower before dehiscence [To prevent self-pollination].
• Bagging: Covering the emasculated flower with a butter-paper bag [To prevent contamination by unwanted pollen].

Step 4: Selection and Testing of Superior Recombinants

This step involves identifying progeny ($F_1$ and subsequent generations) that express the desired combination of traits.

• Self-pollination: The $F_1$ hybrids are selfed for several generations to achieve homozygosity.
• Screening: Large populations are screened for superior phenotypes [Based on Phenotypic Selection principles].

Step 5: Testing, Release, and Commercialization of New Cultivars

The selected lines are subjected to rigorous evaluation for agronomic traits like yield, disease resistance, and nutritional value.

• Research Trials: Evaluation is conducted in research fields under controlled conditions.
• Multi-location Trials: The lines are grown in different agro-climatic zones across the country.
• Final Approval: Once performance is verified, the variety is officially released and distributed to farmers for cultivation.

Final Solution: The plant breeding process is a sequential scientific procedure involving (1) Germplasm collection, (2) Evaluation and parent selection, (3) Cross-hybridization between parents, (4) Selection and testing of superior recombinants, and (5) Field testing and commercial release of the new variety.