Syllabus
Major breeding objectives and procedures including conventional and modern innovative approaches for the development of hybrids and varieties for yield, adaptability, stability, abiotic and biotic stress tolerance and quality (physical, chemical, nutritional) in major Rabi crops
Major Breeding Objectives in Major Rabi Crops:
Breeding in major Rabi crops aims to develop improved varieties and hybrids with specific traits to meet the demands of farmers, consumers, and changing environmental conditions. These breeding objectives vary depending on the crop and its importance in the agricultural sector. Here are the major breeding objectives for some key Rabi crops:
1. Wheat (Triticum aestivum):
- Yield Improvement: Developing varieties with higher grain yield to meet the growing demand for food.
- Disease Resistance: Breeding for resistance against major diseases like rusts, powdery mildew, and leaf spots.
- Abiotic Stress Tolerance: Developing varieties that can withstand drought, heat, and salinity.
- Quality Enhancement: Improving protein content, gluten strength, and baking quality for better end-use.
2. Barley (Hordeum vulgare):
- Yield Enhancement: Breeding for improved yield potential and stability across different environments.
- Disease and Pest Resistance: Developing varieties with resistance to fungal diseases and pests.
- Malting Quality: Improving traits related to malting quality for the brewing industry.
- Adaptation to Different Agro-Climatic Zones: Developing varieties suitable for diverse regions.
3. Chickpea (Cicer arietinum):
- Yield Improvement: Developing high-yielding varieties to enhance chickpea production.
- Disease Resistance: Breeding for resistance to diseases like Fusarium wilt and Ascochyta blight.
- Drought Tolerance: Developing varieties that can withstand water stress and thrive under dry conditions.
- Quality Attributes: Improving cooking time, taste, and nutritional quality.
4. Mustard (Brassica juncea):
- Yield Enhancement: Developing varieties with increased oil content and seed yield.
- Biotic Stress Resistance: Breeding for resistance to diseases like Alternaria blight and insect pests.
- Adaptability to Different Climatic Zones: Developing varieties suitable for diverse regions.
- Oil Quality: Improving the quality of oil in terms of erucic acid and glucosinolates.
5. Lentil (Lens culinaris):
- Yield Improvement: Developing high-yielding varieties to boost lentil production.
- Disease Resistance: Breeding for resistance to diseases like Ascochyta blight and rust.
- Adaptation to Different Agro-Climatic Zones: Developing varieties suitable for various growing conditions.
- Quality Enhancement: Improving cooking time, taste, and nutritional value.
Breeding in major Rabi crops is a dynamic process focused on enhancing productivity, resilience, and quality. The breeding objectives are carefully tailored to the specific needs of each crop and the challenges it faces, such as biotic and abiotic stresses. By continuously developing improved varieties through conventional and modern breeding approaches, plant breeders contribute to sustainable agriculture and food security, addressing the ever-changing demands of the agricultural sector.
Major Breeding Procedures for the Development of Hybrids and Varieties in Major Rabi Crops:
1. Conventional Breeding Approaches:
- Selection: Involves choosing superior plants with desirable traits from a diverse population and using them as parents for the next generation. The process is repeated over multiple generations to fix the desired traits in the offspring.
- Crossing: Controlled pollination between two selected parent plants with complementary traits is done to combine their desirable traits in the offspring.
- Backcrossing: Used to transfer a specific trait from one parent (donor) to an elite variety (recurrent parent). Repeated backcrosses are conducted to recover the recurrent parent's genetic background while retaining the desired trait.
Procedure:
- Initial Cross: Cross the donor parent, which possesses the desired trait, with the recurrent parent, which has desirable agronomic traits but lacks the specific trait.
- Generation BC1: Cross the resulting F1 hybrid back with the recurrent parent (RP). This creates the BC1 generation. Offspring of the BC1 generation now carry half of their genetic material from each parent.
- Selection: Identify individuals from the BC1 generation that exhibit the desired trait from the donor parent. These selected individuals will be used for further backcrossing.
- Subsequent Backcrossing Generations (BC2, BC3, etc.): Continue crossing selected individuals from the previous generation with the recurrent parent. The goal is to progressively transfer the desired trait while minimizing the introduction of donor parent genetic material not related to the trait.
- Marker-Assisted Selection (MAS): In modern breeding, molecular markers associated with the desired trait can be used to assist in selecting individuals that carry the trait, even before it is phenotypically expressed.
- Progressive Recovery of Recurrent Parent's Genetic Background: Over several backcross generations, the proportion of the recurrent parent's genetic background increases, while the introduced trait is retained. This process aims to create plants that resemble the recurrent parent but possess the specific desired trait.
- Field Testing: After multiple rounds of backcrossing, the resulting plants are tested in field trials to ensure that the introduced trait is successfully integrated while maintaining the recurrent parent's desired traits.
- Mass Selection: Bulk harvesting and planting of seeds from a population with desirable traits. The process is repeated for several generations to accumulate the desired traits in the population.
- Pedigree Breeding: Carefully planned crosses between parents with known characteristics, followed by the selection of superior progeny over multiple generations.
Process:
- Selecting Parent Plants: Breeders start with selecting parent plants that have desirable traits. These traits can be related to yield, disease resistance, quality, or any other attribute of interest.
- Crossbreeding: The selected parent plants are crossbred to create the first generation of offspring, referred to as the F1 generation. These offspring inherit genetic material from both parents.
- Selection: Among the F1 generation, breeders carefully evaluate the individuals based on their traits. Individuals with the most desirable combination of traits are selected as parents for the next generation.
- Generation Advancement: The selected individuals from the F1 generation are crossbred again to create the next generation, known as the F2 generation. This process continues in subsequent generations (F3, F4, and so on).
- Continuous Selection: In each generation, breeders continue selecting individuals with the desired traits while discarding those that don't meet the criteria. This gradual selection process aims to improve the overall trait composition of the population.
- Fixing Traits: Over several generations, individuals that consistently exhibit the desired traits are chosen to be parents. This helps "fix" the desired traits in the population, making them more uniform and predictable.
- Progeny Testing: In later generations, selected individuals are evaluated in various environments and conditions to assess their performance and stability. This helps ensure that the desired traits are consistently expressed.
- Line Breeding: Continuous self-pollination of selected superior plants over multiple generations to obtain pure lines with uniform traits.
2. Modern Innovative Approaches:
- Marker-Assisted Selection (MAS): Molecular markers linked to specific genes or traits are used to identify plants with desired characteristics more efficiently. This speeds up the breeding process by reducing the need for laborious phenotypic evaluations.
- Genomic Selection: Whole-genome sequencing and advanced statistical models are used to predict the performance of individuals based on their genomic data. This enables breeders to select plants with desired traits more accurately.
- Transgenic Technology: Genetic engineering is employed to introduce genes from other organisms into crops, conferring resistance to pests, diseases, or tolerance to abiotic stresses.
- Gene Editing: Techniques like CRISPR/Cas9 are used to precisely modify specific genes within a crop's genome, resulting in targeted improvements in desired traits.
- Hybrid Development: Controlled crosses between two genetically diverse parent lines are made to exploit hybrid vigour or heterosis, leading to increased yield and performance in hybrid offspring.
3. Trait-Specific Breeding Objectives:
- Yield Improvement: Selecting parents with high yield potential and employing hybridization to harness heterosis for increased yield.
- Adaptability and Stability: Evaluating candidate varieties across diverse environments to identify those with consistent performance across different regions.
- Abiotic Stress Tolerance: Identifying genes associated with stress tolerance and incorporating them into breeding programs.
- Biotic Stress Resistance: Conduct screenings to identify plants with resistance to major pests and diseases and use them as parents in breeding programs.
- Quality Enhancement: Selecting parents with superior quality traits and conducting targeted crosses to enhance the desired quality attributes.
Breeding approaches for major Rabi crops encompass a combination of conventional and modern innovative techniques to develop hybrids and varieties with improved traits. Through rigorous selection, controlled crossing, and advanced molecular methods, breeders strive to enhance crop productivity, resilience to stresses, and quality attributes.
📚 For comprehensive notes on other chapters of the subject, please visit the website Agricorn - Crop Improvement - II (Rabi Crops).
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