Text Book Back Questions and Answers - Chapter 9 Plant Breeding 12th Biology Botany Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

Updated By SaraNextGen

On April 24, 2024, 11:35 AM

Plant Breeding
Text Book Back Questionsand Answers
Question 1.
Assertion: Genetic variation provides the raw material for selection.
Reason: Genetic variations are differences in genotypes of the individuals.
(a) Assertion is right and reason is wrong.
(b) Assertion is wrong and reason is right.
(c) Both reason and assertion is right.
(d) Both reason and assertion is wrong.
Answer:
(c) Both reason and assertion is right.
Question 2.
While studying the history of domestication of various cultivated plants recognized earlier.
(a) Centres of origin
(b) Centres of domestication
(c) Centres of hybrid
(d) Centres of variation
Answer:
(a) Centres of origin
Question 3.
Pick out the odd pair.
(a) Mass selection - Morphological characters
(b) Purline selection - Repeated self pollination
(c) Clonal selection - Sexually propagated
(d) Natural selection - Involves nature
Answer:
(a) Mass selection - Morphological characters

Question 4.

(a) $i-\mathrm{I}, i i-\mathrm{II}, i i-\mathrm{III}, i v-\mathrm{IV}$
(b) $i$-III, $i i-\mathrm{I}, i i-\mathrm{IV}, i v-\mathrm{II}$
(c) $i$-IV, $i i-\mathrm{II}, i i-\mathrm{I}, i v-\mathrm{IV}$
(d) $i-\mathrm{II}, i i-\mathrm{IV}, i i-\mathrm{III}, i v-\mathrm{I}$
Answer:
(b) i - III, ii - I, iii - IV, iv - II
Question 5.
The quickest method of plant breeding is
(a) Introduction
(b) Selection
(c) Hybridization
(d) Mutation breeding
Answer:
(d) Mutation breeding
Question 6.
Desired improved variety of economically useful crops are raised by
(a) natural selection
(b) hybridization
(c) mutation
(d) biofertilisers
Answer:
(b) hybridization
Question 7.
Plants having similar genotypes produced by plant breeding are called
(a) clone
(b) haploid
(c) autopolyploid
(d) genome
Answer:
(a) clone

Question 8.
Importing better varieties and plants from outside and acclimatising them to local environment is called
(a) cloning
(b) heterosis
(c) selection
(d) introduction
Answer:
(d) introduction
Question 9.
Dwarfing gene of wheat is
(a) pall
(b) Atomita 1
(c) Norin 10
(d) pelita 2
Answer:
(c) Norin 10
Question 10 .
Crosses between the plants of the same variety are called
(a) interspecific
(b) intervarietal
(c) intravarietal
(d) intergeneric
Answer:
(c) intravarietal
Question 11.
Progeny obtained as a result of repeat self pollination a cross pollinated crop to called
(a) pure line
(b) pedigree line
(c) inbreed line
(d) heterosis
Answer:
(a) pure line
Question 12 .
Jaya and Ratna are the semi dwarf varieties of
(a) wheat
(b) rice
(c) cowpea
(d) mustard

Answer:
(b) rice
Question 13.
Which one of the following are the species that are crossed to give sugarcane varieties with high
sugar, high yield, thick stems and ability to grow in the sugarcane belt of North India?
(a) Saccharum robustum and Saccharum officinarum
(b) Saccharum barberi and Saccharum officinarum
(c) Saccharum sinense and Saccharum officinarum
(d) Saccharum barberi and Saccharum robustum
Answer:
(b) Saccharum barberi and Saccharum officinarum
Question 14.
Match column I (crop) with column II (Corresponding disease resistant variety) and select the correct option from the given codes.

Answer:
(b) ii, i, iii, iv
Question 15.
A wheat variety, Atlas 66 which has been used as a donor for improving cultivated wheat, which is rich in
(a) iron
(b) carbohydrates
(c) proteins
(d) vitamins
Answer:
(c) proteins
Question 16.
Which one of the following crop varieties correct matches with its resistance to a disease?

Answer:
(a) Pusa Komal - Bacterial blight
Question 17.
Which of the following is incorrectly paired?
(a) Wheat-Himgiri
(b) Milch breed - Sahiwal
(c) Rice - Ratna
(d) Pusa Komal - Brassica
Answer:
(d) Pusa Komal - Brassica
Question 18.
Match list I with list II:

Answer:
(b) i-d, ii-c, iii-a, iv-b
Question 19.
Differentiate primary introduction from secondary introduction Answer:
1. Primary Introduction: Primary introduction - When the introduced variety is well adapted to the new environment without any alternation to the original genotype.
2. Secondary Introduction: Secondary introduction - When the introduced variety is subjected to selection to isolate a superior variety and hybridized with a local variety to transfer one or a few characters to them.
Question 20.
How are microbial innocnlants used to increase the soil fertility?
Answer:
Biofertilizers or microbial innoculants are defined as preparations containing living cells or latent cells of efficient strains of microorganisms that help crop plants uptake of nutrients by their interactions in the rhizosphere when applied through seed or soil.
They are efficient in fixing nitrogen, solubilising phosphate and decomposing cellulose. They are designed to improve the soil fertility, plant growth, and also the number and biological activity of beneficial microorganisms in the soil. They are ecofriendly organic agro inputs and are more efficient and cost effective than chemical fertilizers.
Question 21 .
What are the different types of hybridization?
Answer:
Types of Hybridization
According to the relationship between plants, the hybridization is divided into.
1. Intravarietal hybridization - The cross between the plants of same variety. Such crosses are useful only in the self-pollinated crops.
2. Intervarietal hybridization - The cross between the plants belonging to two different varieties of the same species and is also known as intraspecific hybridization. This technique has been the basis of improving self-pollinated as well as cross pollinated crops.
3. Interspecific hybridization - The cross between the plants belonging to different species belonging to the same genus is also called intragenic hybridization. It is commonly used for transferring the genes of disease, insect, pest and drought resistance from one species to another.

Question 22 .
Explain the best suited type followed by plant breeders at present?
Answer:
Mutation breeding represents a new method of conventional breeding procedures as they have the advantage of improving the defect without losing agronomic and quality character in agriculture and crop improvement. Mutation means the sudden heritable changes in the genotype or phenotype of an organism. Gene mutations are of considerable importance in plant breeding as they provide essential inputs for evolution as well as for re-combination and selection. It is the only method for improving seedless crops.
Question 23.
Write a note on heterosis.
Answer:
The superiority of the $\mathrm{F}_1$ hybrid in performance over its parents is called heterosis or hybrid vigour.
Vigour refers to increase in growth, yield, greater adaptability of resistance to diseases, pest and drought. Vegetative propagation is the best suited measure for maintaining hybrid vigour, since the desired characters are not lost and can persist over a period of time. Many breeders believe that its magnitude of heterosis is directly related to the degree of genetic diversity between the two parents. Depending on the nature, origin, adaptability and reproducing ability heterosis can be classified as:
1. Euheterosis- This is the true heterosis which is inherited and is further classified as
2. Mutational Euheterosis - Simplest type of euheterosis and results from the sheltering or eliminating of the deleterious, unfavourable often lethal, recessive, mutant genes by their adaptively superior dominant alleles in cross pollinated crops.
3. Balanced Euheterosis - Well balanced gene combinations which is more adaptive to environmental conditions and agricultural usefulness.
4. Pseudoheterosis - Also termed as luxuriance. Progeny possess superiority over parents in vegetative growth but not in yield and adaptation, usually sterile or poorly fertile.
Question 24.
List out the new breeding techniques involved in developing new traits in plant breeding.
Answer:
New Breeding Techniques (NBT) are a collection of methods that could increase and accelerate the development of new traits in plant breeding. These techniques often involve genome editing, to modify DNA at specific locations within the plants to produce new traits in crop plants. The various methods of achieving these changes in traits include the following.
- Cutting and modifying the genome during the repair process by tools like CRISPR/Cas.
- Genome editing to introduce changes in few base pairs using a technique called Oligonucleotide-directed mutagenesis (ODM).
- Transferring a gene from an identical or closely related species (cisgenesis).
- Organising processes that alter gene activity without altering the DNA itself (epigenetic methods)