CBSE Class 12 Biology Chapter 9 Notes: Strategies For Enhancement In Food Production

Key Definitions

Plant Breeding

The purposeful manipulation of plant species to create desired plant types that are better suited for cultivation, give better yields, and are disease resistant.

Biofortification

Breeding crops with higher levels of vitamins, minerals, or higher protein and healthier fats to improve public health.

Inbreeding Depression

The reduction in fertility and productivity observed after continuous inbreeding, especially close inbreeding, in animals.

Outcrossing

A type of outbreeding involving the mating of unrelated animals within the same breed, but having no common ancestors on either side of their pedigree for 4-6 generations.

Micropropagation

The method of producing thousands of plants through tissue culture. Each plant produced this way is genetically identical to the original plant from which it was grown, known as a somaclone.

Somatic Hybridization

The process of fusing isolated protoplasts (plant cells without cell walls) from two different varieties of plant, each having a desirable character, to obtain a hybrid protoplast which can then grow into a new plant.

Single Cell Protein (SCP)

Protein-rich biomass produced by microorganisms like algae, fungi, bacteria, and yeast, used as a protein supplement for human food or animal feed.

Totipotency

The capacity of a plant cell to differentiate into a whole plant, a fundamental principle underlying plant tissue culture.

Multiple Ovulation Embryo Transfer (MOET)

An advanced breeding method for cattle, involving hormone-induced superovulation, artificial insemination, and non-surgical embryo recovery and transfer to surrogate mothers.

Understanding Plant Breeding for Crop Improvement

Plant breeding is a systematic process aimed at developing new crop varieties with desirable traits such as increased yield, improved quality, disease resistance, and tolerance to environmental stresses. This field played a pivotal role in the Green Revolution, significantly boosting food grain production in India. The basic steps involved in a typical plant breeding program are:

1. Collection of Variability (Germplasm Collection): This is the foundation of any breeding program. It involves collecting all the different wild varieties, species, and relatives of the cultivated crop. The entire collection of plants and seeds having all the diverse alleles for all genes in a given crop is called germplasm collection. This genetic diversity is crucial for future breeding efforts.

1. Evaluation and Selection of Parents: The collected germplasm is thoroughly evaluated to identify plants with desirable combinations of traits. These selected plants are then multiplied and used as parents in the breeding program.

1. Cross-hybridization among Selected Parents: Desirable traits from two different parents are often combined through cross-hybridization. Pollen grains from the desired male parent are collected and transferred to the stigma of the female parent (whose anthers have been removed – emasculation). This process aims to combine superior traits from two different lines.

1. Selection and Testing of Superior Recombinants: From the progeny of the hybrids, plants with the desired combination of characters (superior recombinants) are selected. Self-pollination of these selected plants for several generations ensures homozygosity (genetic purity) so that the traits do not segregate in subsequent generations.

1. Testing, Release, and Commercialization of New Cultivars: The selected lines are thoroughly tested under various environmental conditions across different agricultural fields. Their performance in terms of yield, resistance to diseases, and other quality parameters is evaluated. Once a new variety is found to be superior to the existing ones, it is named and released for cultivation to farmers. This entire process is labor-intensive and time-consuming, often taking years to develop a successful new variety.

Animal Breeding Strategies: Inbreeding vs. Outbreeding

Key Examples of Enhanced Food Production

• Improved Crop Varieties 1. Wheat (Kalyan Sona, Sonalika): High-yielding, disease-resistant varieties developed in India after the Green Revolution. 'Atlas 66' is a biofortified wheat variety with high protein content. 2. Rice (Jaya, Ratna): Semi-dwarf varieties developed in India, significantly contributing to increased rice production. 3. Maize: Hybrid maize varieties developed for higher yields, disease resistance, and enhanced amino acid content (lysine and tryptophan).
• Biofortified Crops 1. Iron-fortified rice: Developed to combat iron deficiency, a common nutritional problem. 2. Vitamin A enriched carrots & spinach: Aimed at addressing vitamin A deficiency, especially in children. 3. Protein-enriched beans: Specific varieties of beans developed to provide higher protein levels.
• Superior Animal Breeds 1. Hisardale: A new breed of sheep developed in Punjab by crossing Bikaneri ewes and Merino rams, known for good quality wool and meat. 2. Karan Swiss: A cross-breed of Sahiwal and Brown Swiss cattle, known for high milk yield.

Key Points to Remember

• The Green Revolution was largely dependent on plant breeding techniques for high-yielding and disease-resistant varieties of wheat and rice.
• Disease resistance in crops (e.g., rust-resistant wheat, Pusa Swarnim mustard) and pest resistance (e.g., Pusa Gaurav Brassica for aphids) are critical for sustainable agriculture.
• Biofortification is a crucial strategy to combat 'hidden hunger' (malnutrition due to micronutrient deficiencies) by breeding nutritionally superior crops.
• In animal breeding, inbreeding helps fix desirable traits and achieve homozygosity, but prolonged inbreeding leads to inbreeding depression.
• Outcrossing is the best breeding method for animals that are below average in productivity in milk production or growth rate.
• MOET (Multiple Ovulation Embryo Transfer) is an advanced technique for rapid multiplication of superior female cattle and increasing herd size.
• Micropropagation (plant tissue culture) allows rapid production of genetically identical plants (somaclones) from small plant parts (explants).
• Somatic hybridization involves fusing protoplasts to create novel plant hybrids, like 'Pomato' (though not commercially successful yet).
• Single Cell Protein (SCP), often from Spirulina or Methylophilus methylotrophus, provides a cost-effective, protein-rich supplement for food and feed.

Exam Tip: Focus on Specific Examples and Distinctions

For this chapter, board examiners often look for specific examples of improved crop varieties (e.g., 'Atlas 66' wheat for protein, 'Pusa Swarnim' for disease resistance) and animal breeds (e.g., 'Hisardale' sheep). Make sure you can clearly distinguish between inbreeding and outbreeding, and understand the purpose and outcome of each. Questions on the steps of plant breeding or the application of MOET and micropropagation are common. Pay attention to the advantages of biofortification and SCP in addressing global food challenges. Memorize key terms like 'totipotency' and 'explant' for tissue culture.

Practice Questions with Solutions

• Q: What is biofortification? Give one example of a biofortified crop. A: Biofortification is the breeding of crops with higher levels of vitamins, minerals, protein, or healthier fats. An example is 'Atlas 66' wheat, which has high protein content.
• Q: Differentiate between outcrossing and cross-breeding. A: Outcrossing is mating unrelated animals within the same breed without common ancestors for 4-6 generations. Cross-breeding involves mating two different breeds.
• Q: How is Single Cell Protein (SCP) beneficial for humans? A: SCP serves as a rich source of protein, vitamins, minerals, and fats, helping to reduce the gap between demand and supply of protein and alleviate malnutrition.
• Q: What is the significance of explant and totipotency in plant tissue culture? A: An explant is any part of a plant taken and grown in a test tube under sterile conditions. Totipotency is the inherent capacity of the explant's cells to generate a whole plant. These two concepts are fundamental for micropropagation.

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