Strategies for Enhancement in Food Production: Class 12 Biology NCERT Guide

Core Strategies: Animal Husbandry and Plant Breeding

To boost food production, we apply two major scientific strategies: managing and breeding animals (Animal Husbandry) and manipulating crop plants (Plant Breeding). Animal husbandry is the agricultural practice of breeding and raising livestock. It's not just about keeping animals; it involves professional management of farms, like dairy and poultry farms, to improve yield and quality. A key part of this is Animal Breeding, which aims to increase the yield of animals and improve the desirable qualities of the produce. For instance, breeding for cows that produce more milk or chickens that lay more eggs.

On the other side, Plant Breeding is the purposeful manipulation of plant species to create desired plant types that are better suited for cultivation, give better yields, and are disease-resistant. This is a systematic process involving the collection of genetic variability, evaluation of parent plants, cross-hybridisation, and rigorous testing to release new, improved cultivars. Both these pillars are fundamental to the Green Revolution and our ongoing efforts for food security.

Key Terminology in Food Production Strategies

Animal Breeding

The science and art of genetically improving livestock. It aims to improve desirable characteristics like growth rate, milk/meat/egg production, and disease resistance.

Inbreeding

Mating of more closely related individuals within the same breed for 4-6 generations. It increases homozygosity and helps accumulate superior genes, but can lead to inbreeding depression.

Out-crossing

Mating of animals within the same breed, but having no common ancestors on either side of their pedigree for 4-6 generations. It is the best method to overcome inbreeding depression.

Cross-breeding

Mating superior males of one breed with superior females of another breed. The progeny, called hybrids, often have desirable qualities of both parent breeds (e.g., Hisardale sheep).

Biofortification

The process of breeding crops with higher levels of vitamins, minerals, proteins, or healthier fats. The goal is to improve the nutritional quality of food and combat malnutrition.

Single Cell Protein (SCP)

The production of microbial biomass (like bacteria, yeast, or algae) that is rich in protein and can be used as a food or feed supplement. Example: Spirulina.

The Process of Multiple Ovulation Embryo Transfer (MOET)

1. Step 1: Superovulation — A high-quality 'elite' cow is administered hormones with FSH-like activity. This induces follicular maturation and causes 'superovulation' – instead of producing one egg per cycle, she produces 6-8 eggs.
2. Step 2: Mating/Insemination — The superovulated cow is either mated with an elite bull or artificially inseminated with high-quality semen.
3. Step 3: Embryo Recovery — The fertilised eggs, now at the 8-32 cell stage (embryos), are recovered non-surgically from the genetic mother.
4. Step 4: Embryo Transfer — Each recovered embryo is transferred to a different 'surrogate' mother. The surrogate mothers carry the embryos to term.
5. Step 5: Repetition — The original genetic mother is now available for another round of superovulation, allowing for rapid multiplication of desirable genetics in a short time.

Worked Examples of Plant Breeding Successes

• Example 1: Creating Disease-Resistant Wheat Goal: Develop a wheat variety resistant to leaf and stripe rust, common fungal diseases. Method: Hybridisation and Selection. Parents: A local wheat variety with good yield and a donor variety with genes for rust resistance. Result: The variety Himgiri was developed. It possesses high yield characteristics and is resistant to leaf and stripe rust, and hill bunt disease. This significantly reduced crop loss for farmers.
• Example 2: Developing Insect-Resistant Brassica (Rapeseed Mustard) Goal: Create a mustard variety resistant to aphids, a major insect pest. Method: Hybridisation and Selection. Parents: A high-yielding Brassica variety and a donor parent having genes for hairiness on leaves (a trait that deters aphids). Result: The variety Pusa Gaurav was developed. Its hairy leaves provide resistance against aphids, reducing the need for chemical pesticides.
• Example 3: Biofortification in Maize Goal: Develop a maize hybrid with improved nutritional quality. Method: Breeding for specific nutritional content. Focus: Increase the content of essential amino acids, lysine and tryptophan. Result: Maize hybrids were developed that had twice the amount of lysine and tryptophan compared to existing maize varieties. This helps combat protein malnutrition in populations that rely heavily on maize as a staple food.

Exam Traps and Key Distinctions

A common point of confusion for students is the difference between various animal breeding methods. Remember:

• Out-crossing: Same breed, no common ancestors. Its primary goal is to fix inbreeding depression.
• Cross-breeding: Different breeds. Its goal is to combine desirable traits from two different breeds into one hybrid animal (e.g., Hisardale sheep from Bikaneri ewes and Marino rams).
• Interspecific Hybridisation: Different but related species (e.g., male donkey + female horse → mule). The offspring are almost always sterile.

For plant breeding, always remember the five sequential steps: 1. Collection of variability, 2. Evaluation and selection of parents, 3. Cross hybridisation among selected parents, 4. Selection and testing of superior recombinants, and 5. Testing, release and commercialisation of new cultivars. Questions often ask you to list these steps in order.

Practice Questions with Solutions

• Q: A farmer notices that his herd of purebred cows has reduced fertility and milk yield after several generations of mating within the herd. Which animal breeding technique would you recommend to solve this issue and why? A: Step 1: Identify the problem. The symptoms described—reduced fertility and productivity after prolonged close mating—are classic signs of inbreeding depression. Step 2: Recall the solution for inbreeding depression. The recommended strategy to overcome inbreeding depression is to introduce unrelated genetic material from the same breed. Step 3: Name the specific technique. This practice is called out-crossing. It involves mating the affected animals with superior animals of the same breed that have no common ancestors for 4-6 generations. Final answer: The farmer should use out-crossing. This will restore fertility and yield by introducing new genes into the population without changing the breed.
• Q: What is biofortification? Give an example of a biofortified crop and the nutrient it is enriched with. A: Step 1: Define biofortification. Biofortification is the scientific strategy of breeding crops to have higher levels of essential nutrients like vitamins, minerals, proteins, or healthier fats. Step 2: State the objective of biofortification. Its main objective is to improve public health by increasing the nutritional value of staple foods and combating hidden hunger or micronutrient deficiencies. Step 3: Provide a specific example from NCERT. One prominent example is the development of Atlas 66, a wheat variety. It has been bred to have a significantly higher protein content compared to conventional wheat varieties. Final answer: Biofortification is the breeding of crops to increase their nutritional value. An example is the Atlas 66 wheat variety, which is biofortified for high protein content.
• Q: List the five main steps involved in developing a new plant variety through classical plant breeding. A: Step 1: Recall the first step which is the foundation of any breeding program. The first step is the Collection of variability (germplasm collection). This involves collecting all wild varieties, species, and relatives of the cultivated species to capture the entire set of available alleles for all genes. Step 2: Describe the second and third steps involving parent selection and crossing. The second step is Evaluation and selection of parents, where the collected germplasm is evaluated to identify plants with desirable combinations of characters. The third step is Cross hybridisation among the selected parents to combine the desired characters from two different parents into a single plant. Step 3: Explain the final two steps of selection and release. The fourth step is Selection and testing of superior recombinants, which is a crucial and time-consuming process of selecting offspring with the desired trait combination and self-pollinating them for several generations until they reach a state of uniformity (homozygosity). The final step is Testing, release and commercialisation of new cultivars, where the newly selected lines are evaluated for their yield and other traits in farmers' fields for at least three growing seasons before being released as a new variety. Final answer: The five steps are: 1. Collection of variability, 2. Evaluation and selection of parents, 3. Cross hybridisation among selected parents, 4. Selection and testing of superior recombinants, and 5. Testing, release and commercialisation of new cultivars.
• Q: Why is Multiple Ovulation Embryo Transfer (MOET) considered a valuable program for cattle improvement? A: Step 1: Define MOET's core function. MOET is a technology used to rapidly increase the number of offspring from a genetically superior female (elite cow). Step 2: Explain the 'Multiple Ovulation' advantage. Through hormonal treatment (FSH), the elite cow produces 6-8 eggs instead of one. This multiplies the potential offspring from a single reproductive cycle. Step 3: Explain the 'Embryo Transfer' advantage. The resulting embryos are transferred to surrogate mothers. This frees up the elite genetic mother to be superovulated again quickly, without having to go through a full pregnancy. This shortens the generation interval. Final answer: MOET is valuable because it allows for the rapid multiplication of desirable genetics. It increases the herd size of high-quality animals in a much shorter time than conventional breeding by producing multiple offspring per cycle from an elite female and using surrogate mothers to carry them to term.

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