NEET Biology Plant Breeding MCQs Set 03

Answer: (a) Removal of anthers

Explanation:
1. Emasculation means removing the anthers (male parts) of a bisexual flower before they shed pollen.
2. This prevents self-pollination so that only the chosen pollen is used in the cross.

Teacher's Note:
1. Emasculation is followed by bagging, then dusting with pollen from the selected male parent.
2. Removing the stigma would make seed formation impossible.

Answer: (b) All plant cells

Explanation:
1. Totipotency is the ability of a cell to regenerate a whole plant.
2. Every living plant cell has the full genome and, under suitable culture conditions, can do this.

Teacher's Note:
1. This is the principle behind plant tissue culture.
2. Animal cells are generally not totipotent in this sense.

Answer: (b) Vegetative propagation gives clones, so the hybrid combination is copied without segregation

Explanation:
1. In sexual reproduction heterozygous hybrids segregate and lose their vigour in later generations.
2. In vegetative propagation the offspring are clones of the parent, so the hybrid genotype and its vigour are maintained and multiplied quickly.

Teacher's Note:
1. Hybrid seeds of maize must be bought afresh each season for the same reason.
2. Cloning fixes heterosis.

Answer: (d) Both somatic hybrid and allopolyploid

Explanation:
1. Pomato was produced by fusing protoplasts of potato and tomato.
2. The fused cell contains the chromosomes of both species, so it is a somatic hybrid that is also an allopolyploid.

Teacher's Note:
1. The plant did not become commercially useful because it did not have the desired tomato and potato traits together.
2. Fusion agents include polyethylene glycol.

Answer: (c) Explant

Explanation:
1. An explant is any piece of tissue or organ taken from a plant and grown in sterile culture.
2. A callus is the mass of cells that forms from it, and scion and stock belong to grafting.

Teacher's Note:
1. Explants can be leaf, stem, meristem or anther pieces.
2. Culture is done in a sterile nutrient medium.

Answer: (c) Shoot tip (meristem) culture

Explanation:
1. Apical and axillary meristems are not yet linked to the vascular system, so viruses are generally absent there.
2. Culturing the shoot tip therefore gives virus-free plantlets.

Teacher's Note:
1. This is used to clean up banana, sugarcane and potato stock.
2. Grafting can carry viruses from the scion.

Answer: (b) Benzyl amino purine (BAP)

Explanation:
1. A high cytokinin to auxin ratio promotes shoot formation in callus.
2. BAP is a cytokinin.

Teacher's Note:
1. A high auxin ratio instead promotes roots.
2. 2,4-D is an auxin used to induce callus.

Answer: (c) Genetic variability

Explanation:
1. Breeders can select only where there are differences in the characters.
2. Genetic variability is therefore the starting point; the germplasm collection provides it.

Teacher's Note:
1. Germplasm is the whole collection of alleles of a crop.
2. No variability means no selection.

Answer: (d) Saccharum officinarum

Explanation:
1. Saccharum officinarum is the thick, sugar-rich southern cane.
2. The northern cane S. barberi has thin stems and poor sugar, and crossing the two gave a thick, high-sugar hybrid suited to the north.

Teacher's Note:
1. Remember: officinarum gives sugar, barberi gives hardiness.
2. The hybrid was a classic example of crossing for yield.

Answer: (d) A, B and D

Explanation:
1. A, B and D are correct.
2. C is false because micropropagated plants are somaclones, genetically identical to the parent.

Teacher's Note:
1. Somaclones are identical; somaclonal variation is the exception.
2. IR-8 came from IRRI, Philippines.

Answer: (a) Mung bean

Explanation:
1. In mung bean, resistance to yellow mosaic virus and powdery mildew was induced by mutation breeding.
2. Bhindi got its resistance by transfer from a wild species instead.

Teacher's Note:
1. Mutations are induced by gamma rays or chemicals.
2. Mutation breeding is used when the needed allele is absent from the germplasm.

Answer: (c) C, E, A, D, B

Explanation:
1. First variability is collected (C), then parents are evaluated and selected (E).
2. Next comes the cross (A), then superior recombinants are selected and tested (D), and finally the cultivar is tested, released and commercialised (B).

Teacher's Note:
1. Mnemonic: collect, evaluate, cross, select, release.
2. The testing in farmers' fields lasts at least three seasons.

Answer: (a) Wheat

Explanation:
1. Borlaug developed the high-yielding semi-dwarf wheat varieties of the Green Revolution.
2. Sonalika and Kalyan Sona were later introduced in India.

Teacher's Note:
1. Borlaug is the father of the Green Revolution; Swaminathan is its father in India.
2. Dwarf varieties resist lodging under heavy fertiliser.

Answer: (b) Cross hybridisation among the selected parents

Explanation:
1. Cross hybridisation needs emasculation, bagging and hand pollination, and the desired combination of characters rarely appears.
2. It therefore takes a lot of time and effort.

Teacher's Note:
1. Success of the cross is often low.
2. Testing then takes several more seasons.

Answer: (d) Brassica, Pusa Sem 2, Shoot and fruit borer

Explanation:
1. Pusa Gaurav is the aphid-resistant variety of Brassica (rapeseed mustard).
2. Flat bean varieties Pusa Sem 2 and Pusa Sem 3 resist jassids, and okra Pusa Sawani resists the shoot and fruit borer.

Teacher's Note:
1. Learn the three insect-resistance examples together.
2. Pusa Shubhra is a cauliflower variety.

Answer: (c) Mustard

Explanation:
1. Vitamin C enriched varieties include bitter gourd, bathua, mustard and tomato.
2. Spinach is rich in iron and calcium, lablab in protein and carrot in vitamin A.

Teacher's Note:
1. Match crop with nutrient.
2. Mustard (bathua too) is the vitamin C example.

Answer: (b) Manila (Philippines)

Explanation:
1. IRRI is in Los Banos near Manila in the Philippines.
2. IR-8 and IR-24 were developed there.

Teacher's Note:
1. Jaya and Ratna were developed later in India.
2. IR-36 helped solve food problems in Asia.