Q.Brown rust of wheat is caused by ______.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Plant Breeding
Plant breeding is the deliberate, purposeful manipulation of plant species to create new types that are better suited to cultivation, give higher yield and resist disease. It has been practised for thousands of years and lies behind nearly every major food crop grown today. Classical plant breeding proceeds through defined steps: collecting genetic variability (the germplasm), evaluating and selecting parents, cross-hybridising the selected parents to combine desirable traits, selecting and testing superior recombinant progeny until they become genetically uniform, and finally testing the new lines in research and farmers' fields over several seasons before release. …
Wheat rust diseases are named for the rust-coloured powdery pustules they produce on leaves, and they are caused by a specific class of pathogen rather than a bacterium or virus. …
(c) fungi — brown/leaf rust of wheat is caused by the rust fungus Puccinia recondita (P.
Brown rust of wheat is a fungal disease caused by Puccinia.
Wheat rust diseases (black/stem rust, brown/leaf rust, yellow/stripe rust) are all caused by species of the rust fungus Puccinia, which are obligate parasites producing rust-coloured (reddish-brown) powdery pustules of spores on the leaf surface, reducing photosynthetic …
Showing the 12 most recent of 17 on this concept.
- CBSE 2025Set F1 markMCQQ.Which of the following is used to induce mutation in crop plants?(a) Gamma rays(b) Alpha rays(c) X-rays(d) Sunrays
›Reveal solutionSolution
Gamma rays are used as the physical mutagen in mutation breeding of crops.
Mutation breeding deliberately induces heritable variation so that useful new traits (disease resistance, dwarfness, higher yield) can be selected. Gamma rays are a highly penetrating, high-energy ionising radiation and are the mutagen most widely used to treat seeds/plant material for this purpose. Although X-rays and alpha rays are also ionising, gamma rays are the …
- CBSE 2023Set ANNUAL1 markQ.How is the use of 'Sonalika' variety of wheat helpful in increasing the yield?
›Reveal solutionSolution
Sonalika, a semi-dwarf, disease-resistant, early-maturing wheat variety from the Green Revolution, boosted yield mainly by resisting lodging under heavy fertiliser use.
Sonalika is one of the high-yielding wheat varieties developed in India as part of the Green Revolution, using semi-dwarf wheat germplasm originally introduced from Mexico (associated with Dr Norman Borlaug's breeding programme). Being semi-dwarf, it has a short, strong stem that does not fall over (lodge) even when it produces a heavy grain head and is grown with generous doses of fertiliser and irrigation — a major limitation of earlier tall varieties, which would lodge under such conditions and lose yield. It is also comparatively rust-resistant and early-maturing, allowing farmers to harvest sooner and so …
- CBSE 2023Set ANNUAL1 markMCQQ.Which plant breeding method is used by human from ancient time?(a) Hybridization(b) Selection(c) Mutation(d) None of these
›Reveal solutionSolution
Selection — repeatedly choosing and propagating plants with desirable traits from a mixed population — is the oldest plant breeding technique, used by farmers long before genetics was understood.
Early farmers, without any knowledge of genetics, improved their crops simply by observation and selection:
- They would identify individual plants in their fields showing desirable characters (higher yield, better grain size, disease resistance, taste), and
- Save and sow the seeds from only those selected plants for the next season, generation after generation. …
- CBSE 2023Set ANNUAL1 markMCQQ.Autopolyploidy can be artificially induced(a) by colchin(b) by chloroform(c) by colchicine(d) by chloroquine
›Reveal solutionSolution
Colchicine induces autopolyploidy.
Colchicine, an alkaloid from Colchicum autumnale, binds tubulin and prevents the assembly of spindle microtubules during cell division. As a result, the duplicated chromosomes are not separated to opposite poles and the cell ends up with a doubled (or multiplied) chromosome set — inducing autopolyploi …
- CBSE 2022Set ANNUAL1 markQ.Why is the South Indian sugarcane preferred by agriculturists?
›Reveal solutionSolution
Saccharum officinarum (South Indian sugarcane) has thicker stems and far higher sugar content than North Indian cane, making it agriculturally preferred.
India grows two broad groups of sugarcane: North Indian canes (largely Saccharum barberi), which are thinner-stemmed with comparatively lower sugar content but are better adapted to the cooler North Indian climate; and South Indian canes (Saccharum officinarum), which have thick, juicy stems and a much higher sugar (sucrose) content, but are less tolerant of North Indian growing conditions. Because sugar yield per plant is the key economic trait for agriculturists, thick-stemmed, high-sucrose South Indian S. officinarum is the more commercially preferred type. In practice, plant breeders hybridise S. officinarum with S. barberi to combine officinarum's superior sugar y …
- CBSE 2022Set ANNUAL1 markMCQQ.Emasculation is related to?(a) mass selection(b) clonal selection(c) hybridization(d) pure line
›Reveal solutionSolution
Emasculation is part of artificial hybridisation in plant breeding, so the answer is (C).
In plant breeding, artificial hybridisation is done to cross two selected parents with desirable traits. When the female parent bears bisexual flowers, its own anthers must be removed before they mature and shed pollen, to prevent self-pollination. This removal of anthers is called emasculation. The emasculated flower is then bagged and later dusted with pollen from the chosen ma …
- CBSE 2022Set ANNUAL1 markMCQQ.Pusa Shubhra is a variety of(a) wheat(b) cauliflower(c) chilli(d) cabbage
›Reveal solutionSolution
Pusa Shubhra is a cauliflower variety, so the answer is (B).
Many improved vegetable varieties have been bred in India for disease and pest resistance. Pusa Shubhra (and Pusa Snowball K-1) are cauliflower varieties resistant to diseases such as black rot and curd blight. These are outcomes of plant br …
- CBSE 2022Set ANNUAL1 markMCQQ.Triticum aestivum, which is a hexaploid wheat, contains(a) 7 chromosomes(b) 14 chromosomes(c) 30 chromosomes(d) 42 chromosomes
›Reveal solutionSolution
Hexaploid wheat has 2n = 42, so the answer is (D).
The basic (monoploid) chromosome number for wheat is x = 7. Common bread wheat, Triticum aestivum, is a hexaploid — it carries six sets of chromosomes. Therefore its chromosome number is 6 × 7 = 42 (2n = 42). Polyploid crops like hexaploid wheat are impo …
- CBSE 2020Set ANNUAL1 markQ.Which variety of Brassica is resistant to Aphid?
›Reveal solutionSolution
The aphid-resistant variety of Brassica (rapeseed-mustard) is Pusa Gaurav.
Among the crop varieties bred for insect-pest resistance, the rapeseed-mustard (Brassica) variety Pusa Gaurav is resistant to aphids. It was developed by conventional plant breeding (hybridisation and selection), enabling the crop to resist aphid infestation and reduce yield losses without relying on chemical insecticides. (This topic belongs to …
- CBSE 2020Set ANNUAL1 markQ.State one Programme to improve chances of successful production of hybrids.
›Reveal solutionSolution
Careful emasculation and bagging of the female parent flower is a key programme step that ensures a hybridisation cross is not contaminated by unwanted pollen.
To successfully produce a hybrid by crossing two selected parent plants in a breeding programme, it is essential to prevent the female parent flower from being pollinated by any unwanted pollen (its own or from an unintended source). This is achieved through emasculation (removing the anthers of the bisexual flower before they mature and shed pollen) followed by bagging (covering the emasculated flower with a bag to exclude all other pollen carried by wind/insects), and later, deliberately dusting the stigma with the desired pollen from the selected male parent — this careful, controlled procedure greatly improves the …
- CBSE 2019Set ANNUAL1 markMCQQ.Which one of the following is an exotic fish?(a) Labeo rohita(b) Cyprinus carpio var. communis(c) Tilapia massambica(d) Both(b) and (c)
›Reveal solutionSolution
Exotic fishes are those introduced from other countries; both common carp and Tilapia are exotic, so the answer is (d).
An exotic fish is a species brought into India from a foreign country (as opposed to an indigenous/native one).
- (a) Labeo rohita (Rohu) — an indigenous Indian major carp.
- (b) Cyprinus carpio var. communis (common carp) — introduced from Europe/Asia → exotic. …
- CBSE 2019Set ANNUAL1 markQ.What is Biofortification?
›Reveal solutionSolution
Biofortification = breeding crop plants for improved nutritional quality (more vitamins, minerals, proteins) to combat 'hidden hunger'.
Biofortification is a plant-breeding strategy for improving the nutritional value of food crops. Breeders develop varieties with higher content of vitamins and minerals, better-quality proteins, and healthier oils, so that ordinary staple crops themselves supply more nutrition and help fight micronutrient malnutrition ('hidden hunger') in the population.
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