Agricultural Science and Technology

• Statement 1 is correct. Bagasse is the fibrous residue left after cane is crushed and juice extracted, and it is burnt in the mill's own boilers to raise steam and generate power. Indian sugar mills are cogeneration units for this reason, many of them exporting surplus power to the grid, and bagasse is also a feedstock for paper and particle board.
• Statement 2 is incorrect, and this is the tested item. Molasses is the viscous residue left after sucrose crystallisation, and its uses are fermentative and nutritional: potable and industrial alcohol, ethanol, yeast, citric and acetic acid, and cattle feed. Synthetic chemical fertilizers are made from wholly different feedstocks, ammonia synthesised from natural gas or naphtha for nitrogenous fertilizers, rock phosphate for phosphatic and mined potash for potassic. The word synthetic is decisive: press mud and spent wash from distilleries are indeed returned to the field as organic manure, but that is a bio manure route, not the manufacture of a synthetic chemical fertilizer.
• Statement 3 is correct and is the basis of the Ethanol Blended Petrol Programme, molasses being the principal Indian ethanol feedstock at the time this paper was set. The official answer (c), one and three only, follows. There is no elimination route: the candidate must adjudicate statement 2 on its own, since statements 1 and 3 are both secure and the option set splits precisely on it.

• Item 1, Agaricus, is not a biofertilizer. It is the genus of the common button mushroom, a saprophytic basidiomycete grown for food on composted substrate. The fungi that do serve as biofertilizers are the mycorrhizal symbionts, Glomus and the other arbuscular mycorrhizal genera, which extend the absorptive reach of the root and mobilise phosphorus, and Agaricus forms no such association with crop roots.
• Item 2, Nostoc, is a biofertilizer and is the securest item in the set. It is a filamentous cyanobacterium with specialised heterocysts, the thick walled anaerobic cells in which nitrogenase fixes atmospheric nitrogen, and it is one of the standard blue green algal inoculants for wetland paddy alongside Anabaena, Aulosira and Tolypothrix.
• Item 3, Spirogyra, is a filamentous green alga of freshwater bodies with the characteristic helical chloroplast. It fixes no nitrogen. Its claim to the label rests on the broader sense in which algal biomass added to a paddy field contributes organic matter, and on its presence in mixed algal preparations, which is why the official key accepts it. Taking items 2 and 3, the official answer is (c). The elimination route disposes of half the option set and no more: Agaricus removes option (a) and Nostoc removes option (d), after which the choice between (b) and (c) rests wholly on Spirogyra, with no second fact available to settle it.

• Option (b) is correct. Guar gum is a galactomannan polysaccharide obtained from the endosperm of the cluster bean seed. In water it hydrates to give very high viscosity at low concentration, and it is cross-linked with borate or metal ions to form the gel that carries proppant, usually sand, into the fractures opened by hydraulic fracturing, holding them apart after pressure is released; a breaker is then used to degrade the gel so that the gas can flow. The expansion of shale gas production in the United States accordingly generated an enormous derived demand for Indian guar, which is grown chiefly in Rajasthan, Haryana and Gujarat, and prices rose sharply in 2012.
• Option (a) is incorrect: the commercial product of the seed is the gum from the endosperm, not an oil, and biodegradable plastics are made from starch, polylactic acid and polyhydroxyalkanoates.
• Option (c) is incorrect: no antihistamine property of the leaf is the reason for the crop's new significance.
• Option (d) is incorrect: guar is not a biodiesel feedstock, that role in India belonging to jatropha, pongamia and used cooking oil. The stem itself supplies the route, since it says the recent significance is new and commercial, and only option (b) names an industrial demand that arose recently.

• Statement 1 is correct. Neem oil and neem seed kernel extract contain azadirachtin and related limonoids, which act as antifeedants, oviposition deterrents and insect growth regulators, disrupting moulting by interfering with ecdysteroid function; they are effective against a wide range of chewing and sucking insects and against mites, and the mode of action makes resistance slow to develop.
• Statement 3 is correct. Neem oil and its fractions are used in antiseptic, antifungal and dermatological preparations, and nimbidin and related compounds are the subject of a large pharmacological literature. The key treats statement 2 as incorrect and answers (c). The rejection has to rest on the statement being compound: it asserts both biofuel manufacture and hospital detergent manufacture, and if either limb fails the whole fails. On the key's reading, neem seed oil as a biodiesel feedstock is a laboratory and pilot proposition rather than a manufacturing reality, and hospital detergent is not a recognised neem product line.
• Statements 1 and 3 are both secure, so eliminating either is impossible; the item is decided wholly on statement 2, between (c) and (d), with (a) and (b) removed by the security of statements 3 and 1 respectively.

• Statements 1 and 3 are correct and statement 2 is incorrect, so the official answer is (c).
• Statement 1 is correct by definition: vegetative propagation proceeds by mitosis from somatic tissue of a single parent, so the progeny are genetically identical to the parent and to one another, which is what a clone is, and this is precisely why it is used for fruit crops where a desirable genotype must be preserved unchanged.
• Statement 3 is correct: because propagation does not depend on flowering, pollination or seed set, it is not confined to a reproductive season, and cuttings, layering, budding and grafting can be carried out over much of the year subject only to the physiological condition of the stock and scion.
• Statement 2 is incorrect and is the pivot of the item. Vegetative propagation perpetuates viruses rather than eliminating them, because most plant viruses are systemic and move through the vascular system, so any cutting, tuber, sucker or scion taken from an infected plant carries the infection with it; this is why virus accumulation over successive vegetative generations is a standing problem in potato, sugarcane, banana and citrus. The technique that does eliminate virus is meristem tip culture, and the reason it works is instructive: the apical meristem has no differentiated vascular tissue, its cells divide rapidly and outpace viral movement, and a sufficiently small excised tip is therefore usually virus-free.

All three are correct, so the official answer is (d).

• Statement 1 is correct and is the largest industrial use of the grain: the maize kernel is roughly seventy per cent starch by weight, and wet milling separates it into starch, germ, gluten and fibre, the starch going on to modified starches, dextrose, high fructose syrup and a large range of food and industrial products.
• Statement 2 is correct: maize germ, separated in milling, yields corn oil, and any triglyceride oil can be transesterified with a short-chain alcohol to give fatty acid methyl esters, which is biodiesel. Whether it is economic to use an edible oil for the purpose is a separate question from whether it is technically a feedstock, and the statement claims only the latter.
• Statement 3 is correct: the starch is hydrolysed to fermentable sugars and fermented by yeast, which is the basis both of maize-based spirits such as bourbon and of fuel ethanol, the two differing in purification rather than in the underlying process. The item is answered by recognising maize as a starch crop and then reasoning that a starch crop with an oil-bearing germ necessarily supports all three uses, so no recall of an industrial list is needed.

Neem coating works through the nitrification-inhibiting action of neem's triterpenoids, chiefly azadirachtin and related limonoids, which suppress the ammonia-oxidising bacteria that convert ammonium to nitrate. The practical effect at field level is that urea hydrolyses and becomes plant-available more slowly, so nitrogen release is spread across the crop's uptake period rather than flushed in a pulse. That reduces leaching and volatilisation losses, raises nitrogen use efficiency and, incidentally, makes the urea unpalatable for diversion to industrial uses.

• Option (b) captures this and is correct.
• Option (a) inverts the mechanism: neem does not increase microbial nitrogen fixation, it inhibits nitrifying microorganisms, and in any event fixation converts atmospheric nitrogen and is irrelevant to applied urea.
• Option (c) is wrong on an absolute qualifier: slowing nitrification reduces nitrous oxide emissions from fertilised fields but cannot eliminate them, and 'not at all' is untenable for any agricultural practice.
• Option (d) is a straightforward fabrication, neem coating being neither a weedicide nor crop-specific. The elimination route is that (c) and (d) fail on their own terms without any knowledge of neem chemistry, leaving a choice between two microbiological claims of opposite sign.

All three uses are established and the official answer (d) follows.

• Statement 1 is correct: sequencing identifies molecular markers, single nucleotide polymorphisms and quantitative trait loci linked to traits such as disease resistance and drought tolerance, which is the foundation of marker assisted selection.
• Statement 2 is correct and follows directly from statement 1: conventional breeding requires each generation to be grown to maturity and phenotyped, whereas marker assisted and genomic selection allow a breeder to screen seedlings at the DNA level and discard unwanted genotypes before field evaluation, and to track a recessive or difficult to phenotype trait through backcrosses, compressing the breeding cycle substantially.
• Statement 3 is correct: sequencing both host and pathogen genomes allows resistance genes to be matched against pathogen effector genes, which is how the gene for gene relationship is now investigated, and permits pathogen races to be tracked as they overcome deployed resistance. Since no statement can be rejected, there is no elimination route, but the item is easy because statement 2 follows logically from statement 1 and statement 3 is a natural extension, so a candidate who accepts the first accepts all three. Governing principle: sequencing yields information, and every legitimate application is an application of information, whether to selection, to acceleration of breeding or to the analysis of interaction.

All four disperse plant pathogens and the answer is (d).

• Item 1 is correct: birds carry spores, bacteria and viruses on feet, feathers and beak from plant to plant, transmit some pathogens through droppings, and create the wounds through which infection enters when they peck at fruit; they also carry infected insect vectors.
• Item 2 is correct: wind blown dust and soil particles carry fungal spores, bacteria, nematode cysts and resting structures over long distances, and abrasion by blown particles also injures leaf surfaces and opens entry points, which is why dust storms precede outbreaks in semi arid cropping systems.
• Item 3 is correct and operates by two distinct mechanisms: rain splash physically ejects spores and bacterial cells from infected tissue and soil onto healthy foliage above, which is the principal short range dispersal route for many bacterial blights and for anthracnose, and prolonged leaf wetness supplies the free water that spores need to germinate and penetrate.
• Item 4 is correct and is the most familiar route, wind carrying rust urediniospores across hundreds of kilometres, which is how wheat rusts move from one region to another between seasons. Since no item can be rejected, only option (d) survives and no elimination is needed. Governing principle: a plant pathogen is immobile and must be carried, so almost any agent that moves material between plants, whether animal, particle, water or air, is a potential means of dissemination.

Hence (d).

• Statement 1 is correct. In the bud chip method only the bud along with a small portion of adjoining cane is scooped out and raised in a nursery, so the remaining cane is available for milling, and seed material requirement falls sharply against conventional planting of two or three budded setts.
• Statement 4 is correct. Micropropagation from meristem tissue is used to multiply disease free planting material rapidly and is standard in seed cane programmes.
• Statements 2 and 3 are both incorrect and both invert the underlying agronomy. A sett with several buds carries more stored food and moisture in the internodes, so it germinates at a higher percentage and survives adverse weather better than a single budded sett, which has a small reserve and desiccates or rots more readily. The answer is 1 and 4, giving (c). The single budded sett is chosen to economise on seed, not because it establishes better, and options (a), (b) and (d) all confuse those two things.

Bollgard is the Monsanto trade name for Bt cotton. Bollgard I carries a single gene, cry1Ac, from Bacillus thuringiensis, expressing a crystal protein toxic to lepidopteran bollworms. Bollgard II stacks two genes, cry1Ac and cry2Ab, which broadens the pest spectrum and, importantly, delays the evolution of resistance, since an insect must acquire resistance to both toxins simultaneously. Both are therefore transgenic crop technologies, making option (b) correct.

• Option (a) is wrong because clonal propagation is tissue culture, involving no gene transfer.
• Option (c) is wrong because plant growth substances are auxins, gibberellins and cytokinins.
• Option (d) is wrong because biofertilisers are microbial inoculants such as Rhizobium and Azotobacter. Hence (b). Bt cotton remains the only GM crop approved for commercial cultivation in India, which is a fact worth stating precisely whenever this topic arises.