Biology Class 12 NCERT Solutions: Chapter 9 Strategies for Enhancement in Food Production Part 3

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Q.7 Briefly describe various steps involved in plant breeding.

Answer:

  • Plant breeding is the process in which two genetically dissimilar varieties are purposely crossed to produce a new hybrid variety. As a result, characteristics from both parents can be obtained in the hybrid plant variety.

  • Thus, it involves the production of a new variety with the desired characteristics such as resistance to diseases, climatic adaptability, and better productivity.

The various steps involved in plant breeding are as follows:

  1. Collection of genetic variability: Genetic variability from various wild relatives of the cultivated species are collected to maintain the genetic diversity of a species. The entire collection of the diverse alleles of a gene in a crop is called the germplasm collection.

  2. Evaluation of germplasm and selection of parents: The germplasm collected is then valuated for the desirable genes. The selected plants with the desired genes are then used as parents in plant breeding experiments and are multiplied by the process of hybridization.

  3. Cross-hybridization between selected parents: The next step in plant breeding is to combine the desirable characters present in two different parents to produce hybrids. It is a tedious job as one has to ensure that the pollen grains collected from the male parent reach the stigma of the female parent.

  4. Selection of superior hybrids: The progenies of the hybrids having the desired characteristics are selected through scientific evaluation. The selected progenies are then self-pollinated for several generations to ensure homozygosity.

  5. Testing, release, and commercialization of new cultivars: The selected progenies are evaluated for characters such as yield, resistance to diseases, performance, etc. by growing them in research fields for at least three growing seasons in different parts of the country. After thorough testing and evaluation, the selected varieties are given to the farmers for growing in fields for a large-scale production.

Q.8 Explain what is meant by biofortification.

Answer:

  • Biofortification is a process of breeding crops with higher levels of vitamins, minerals, proteins, and fat content. This method is employed to improve public health.

  • Breeding of crops with improved nutritional quality is undertaken to improve the content of proteins, oil, vitamins, minerals, and micro-nutrients in crops.

  • It is also undertaken to upgrade the quality of oil and proteins. An example of this is a wheat variety known as Atlas 66, which has high protein content in comparison to the existing wheat.

  • In addition, there are several other improved varieties of crop plants such as rice, carrots, spinach etc. which have more nutritious value and more nutrients than the existing varieties.

Image of Biofortification

Image of Biofortification

Q.9 Which part of the plant is best suited for making virus-free plants and why?

Answer:

  • Apical and axillary meristems of plants is used for making virus-free plants. In a diseased plant, only this region is not infected by the virus as compared to the rest of the plant region.

  • Hence, the scientists remove axillary and apical meristems of the diseased plant and grow it in vitro to obtain a disease-free and healthy plant.

  • Virus-free plants of banana, sugarcane, and potato have been obtained using this method by scientists.

Q.10 What is the major advantage of producing plants by micro propagation?

Answer:

  • Micro propagation is a method of producing new plants in a short duration using plant tissue culture.

  • Some major advantages of micro propagation are as follows:

  • Micro propagation helps in the propagation of a large number of plants in a short span of time.

  • The plants produced are identical to the mother plant.

  • It leads to the production of healthier plantlets, which exhibit better disease-resisting powers.

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