Bihar Board - Class 12 Biology - Chapter 9: Strategies for Enhancement in Food Production Long Answer Question

Q.1. What are the various steps that a Botanist will undertake to release a new variety of plant?

A.1. Following are the steps:

• Collection of variability – Genetic variability is the root of any breeding programme. Preservation and collection of various wild varieties of species and variants of the cultivated species is a primary source for the productive exploitation of natural genes in a population. It has a germplasm collection.

• Selection and Evaluation of parents – The germplasm is assessed to identify plants with desirable traits. The selected plants thus obtained are multiplied and utilized in the process of hybridization. Wherever possible, pure lines are created.

• Cross-hybridization: Desired characters from selected parents are often combined from two different parents. It is a time consuming and a tedious process as pollen grains from the desired male plant have to be collected and placed on the stigma of the selected female plants.

• Selection and Testing of Superior recombinants: Selecting plants having desired trait combination among progeny. It is crucial for the breeding objective and requires a scientific examination of the progeny. It yields plants that are superior to their parents, which are self-pollinated until they reach a state of uniformity so as to not segregate characters in the progeny.

• Testing, commercialization and release of new cultivators

Q.2. In crop improvement programmes, how are tissue culture methods beneficial over conventional methods of plant breeding?

A.2. Tissue culture was developed as the conventional breeding method failed to keep pace with demand and to provide fast and efficient systems for crop improvement sufficiently. Advantages of tissue culture are as follows:

• Produces a large number of plantlets by micropropagation within a short period of time.

• All cells have a similar genotype and constitute a clone as they are derived from a single explant by mitotic division.

• By providing salts, toxins etc tolerance to stress can be obtained in culture medium in increasing dosage. The surviving cells are then selected to raise resistance in plants

• Through meristem culture, virus-free plantlets can be obtained

• From new plants, embryos which do not survive inside seeds can be cultivated by tissue culture

Q.3. Explain the process of somatic hybridization.

A.3. Somatic hybridization takes place in the following steps:

1. Isolation and Fusion: The isolated protoplast is devoid of protoplast. Thus there are no barriers to protoplast fusion. This can be achieved by mechanical, induced or spontaneous fusion methods.

2. Hybrid Selection: After protoplast fusion, a heterogeneous mixture of unfused chloroplast, homokaryons and heterokaryons are obtained. These hybrid cells (heterokaryons) are then selected through biochemical, cytometric and visual methods.

3. Identification of Hybrid Cells: The somatic hybrids are identified by various molecular techniques such as RFLP, AFLP, PCR, etc.

Q.4. What is germplasm? Why is it necessary to have germplasm collection?

Ans: Germplasm is the genetic material that is passed down through the generations via germ cells. It refers to the total number of genes in an individual. It is used as a starting point for the development of various crops by breeders.

The primary goal of germplasm collecting is to preserve genetic variation in a certain plant or genetic stock for future use. 

Benefits of Collecting Germplasm:

• Many plant cell and tissue cultures may be cryopreserved and kept alive for several years before being used when needed.

• This approach can be used to preserve plant components from endangered species.

• It is an ideal way to keep cell cultures that produce secondary metabolites like antibiotics safe for a long time.

• Recalcitrant seeds (seeds that lose viability after being stored) can be kept for a long time.

• Disease-free plant materials can be frozen and propagated as needed.

• In civilizations, somaclonal differences are preserved.

• Rare germplasms created by somatic hybridization and other forms of genetic manipulation can be saved.

Q.5. What are the major steps involved in Plant breeding?

Ans: The steps in plant breeding are;

(i) Variation Collection: the gathering and preservation of all wild variations, species, and relatives of farmed species.

(ii) Germplasm Evaluation & Parent Selection: Germplasm is analyzed to find plants with suitable characteristics. The chosen plants are multiplied and put to use.

(iii) Selected Parent Hybridisation: Selected parents are hybridized so that their qualities can be integrated into the hybrid progeny.

(iv) Selection and Testing of Superior Recombinants: From the progeny, individuals with the required combination of characteristics must be chosen. These hybrids surpass both of their parents.

(v) Testing, Release and Commercialization of New Cultivars:

Growing these plants in a study field and documenting their performance under ideal circumstances of irrigation, fertilizers, and other agriculture techniques are used to evaluate them. The chosen plants are next evaluated for at least three growing seasons in the farmer's field. As a result, the item chosen is certified and published as a variety.

Q.6. What do you mean by "Outbreeding"? What are the different methods employed for outbreeding?

Ans: Outbreeding is the practice of breeding unrelated males as female animals. It can be accomplished in the following ways:

(i) Outcross: An outcross is the mating of animals from the same breed who have no common ancestor on either side of their lineage for 4-6 generations. It is the most effective way of breeding animals with below-average milk output, beef cattle growth rates, and so on.

(ii) Cross-Breeding: This is when superior males of one breed are crossed with superior females of another breed. It permits the beneficial characteristics of two distinct breeds to be blended and used for commercial production, for example, Hisardale, a new breed of sheep produced by combining bikaneri ewes with Marino rams.

(iii) Interspecific Hybridization: male and female animals of two different related species are mated so that offspring might have desired characteristics from both parents, for example, a mule is formed by crossing a donkey and a female horse.

Q.7 What is somatic hybridization - Explain the steps involved in the production of somatic hybrids?

Ans: The technique of fusing protoplasts of somatic cells generated from two distinct kinds or species of a plant on an appropriate nutritional culture medium under sterile conditions is known as somatic hybridization. Topato, a somatic hybrid created by fusing tomato and potato protoplasts, is one example.

The following stages are involved in somatic hybridization:-

(I) Protoplast isolation from two distinct plant types, each with a desired trait,

(II) When the cytoplasm of two protoplasts fuses, the cytoplasm coalesces. Even after cytoplasm fusion, the nuclei of two protoplasts may or may not fuse; protoplast fusion requires a suitable chemical termed fusogen, such as PEG or polyethylene glycol.

(III) Hybrid protoplasts form a new cell wall around themselves when conditions are favorable. A hybrid cell starts freshwater single-cell fish indefinitely to create a callus.

(IV) The callus is regenerated and transferred to fresh culture plates with appropriate culture media.