Agriculture 2022 Paper II 50 marks Discuss

Q2

(a) Discuss the structure of a plant chromosome and its role in genetic diversity. 20 (b) Discuss the concept of centre of origin of crops and its role in plant breeding. Describe the role of N. I. Vavilov in identifying centre of origin of various crops with appropriate examples. 20 (c) What are the factors that affect the longevity of seeds during storage in warehouses? Describe. 10

हिंदी में प्रश्न पढ़ें

(क) पौधों के गुणसूत्र की संरचना और जननिक विविधता में इसकी भूमिका का वर्णन कीजिए। 20 (ख) फसलों के उत्पत्ति-केंद्र की अवधारणा और पादप प्रजनन में इसकी भूमिका का वर्णन कीजिए। विभिन्न फसलों के उत्पत्ति-केंद्रों की पहचान करने में एन० आई० वैविलोव की भूमिका का उपयुक्त उदाहरणों के साथ वर्णन कीजिए। 20 (ग) गोदामों में भंडारण के दौरान बीज के आयुकाल को प्रभावित करने वाले कारक क्या हैं? वर्णन कीजिए। 10

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Directive word: Discuss

This question asks you to discuss. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'discuss' demands a comprehensive, analytical treatment with balanced coverage across all three sub-parts. Allocate approximately 40% of word budget to part (a) on chromosome structure and genetic diversity, 40% to part (b) on Vavilov's centres of origin, and 20% to part (c) on seed storage factors—roughly matching the 20:20:10 mark distribution. Structure with a brief integrated introduction, three distinct substantive sections for each sub-part, and a concluding synthesis linking genetic conservation to food security.

Key points expected

  • Part (a): Eukaryotic chromosome structure—nucleosome organization (histone octamer, DNA wrapping), 30nm fiber, looped domains, centromere-telomere architecture; sources of genetic diversity—crossing over, independent assortment, mutation, polyploidy; significance in crop improvement
  • Part (b): Vavilov's concept of centres of origin and primary/secondary gene centres; eight centres with Indian examples (Hindustan centre—rice, sugarcane, pigeonpea; Indo-Burma centre—mango, citrus); role in plant breeding—source of dominant genes, disease resistance, wide hybridization
  • Part (b): Vavilov's contributions—Law of Homologous Series, differential phylogenetic method, expeditions to 50+ countries; specific examples—wheat in Afghanistan/Persia, maize in Mexico, potato in Peru-Chile centre
  • Part (c): Seed longevity factors—intrinsic (genetic constitution, seed structure, chemical composition, initial quality) and extrinsic (temperature, relative humidity, moisture content, oxygen pressure, storage container, pest management)
  • Part (c): Harrington's rules and Indian storage protocols—NBPGR gene banks, cryopreservation, hermetic storage; link to Seed Vault at Svalbard and Indian regional stations

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Demonstrates precise understanding of nucleosome structure and chromosome organization in (a); accurately distinguishes primary, secondary and micro-centres of origin in (b); correctly applies Vavilov's Law of Homologous Series with appropriate crop examples; precisely states Harrington's rules and critical moisture-temperature relationships in (c)Basic chromosome structure described but missing nucleosome detail; centres of origin listed without clear distinction between primary/secondary; Vavilov mentioned without specific contributions; seed storage factors enumerated without quantitative relationshipsConfuses prokaryotic and eukaryotic chromosome structure; conflates centre of origin with centre of diversity; attributes wrong crops to Vavilov's centres; fundamental errors in seed physiology concepts
Quantitative reasoning15%7.5Applies Harrington's rules quantitatively—seed life halves with 1% moisture increase or 5°C temperature rise; cites chromosome numbers (2n=14 for wheat, 2n=24 for rice) and ploidy levels in genetic diversity explanation; mentions Vavilov's 50+ expeditions and 250,000+ accessionsMentions temperature and moisture importance without specific quantitative relationships; general reference to chromosome numbers without application to diversity; vague reference to Vavilov's collections without scaleNo quantitative data presented; incorrect or invented numbers for chromosome counts, storage parameters, or Vavilov's work
Indian context examples20%10For (a): cites Indian crop diversity—48,000 rice varieties documented by Vavilov in India; for (b): detailed treatment of Hindustan centre (rice, black gram, green gram, pigeonpea, jute, sugarcane) and Indo-Burma centre (citrus, mango, banana); for (c): references NBPGR (National Bureau of Plant Genetic Resources) gene banks at Delhi, Hyderabad, Thrissur and cryopreservation facilitiesMentions India as a centre of diversity without specific crops; general reference to Indian gene banks without naming NBPGR; limited integration of Indian examples across all three partsNo Indian examples provided; or incorrect attribution (e.g., placing wheat origin in India); ignores India's role in genetic resource conservation entirely
Diagram / process20%10Clear labeled diagram of nucleosome structure (histone octamer, 147bp DNA wrapping, H1 linker) for (a); schematic of Vavilov's eight centres on world map with crop symbols for (b); flowchart of seed deterioration process or gene bank storage protocol for (c); all diagrams integrated with explanatory textOne relevant diagram present but poorly labeled or partially accurate; textual description substitutes for visual representation in other parts; diagrams mentioned but not executedNo diagrams despite clear visual components in the question; or diagrams with fundamental errors (e.g., showing DNA outside histones, misplacing centres geographically)
Policy / extension angle20%10Links chromosome-level diversity to Farmers' Rights under PPVFR Act 2001; connects Vavilov's centres to contemporary bioprospecting and ABS (Access and Benefit Sharing) protocols under Nagoya Protocol; discusses National Seed Policy 2002 and Seed Bill provisions for germplasm conservation; mentions Svalbard Global Seed Vault and India's deposit of 1.5 lakh accessionsGeneral mention of genetic resource conservation importance; reference to seed banks without policy context; limited connection between historical Vavilov work and current Indian legislationNo policy or extension perspective; treats question as purely academic exercise without real-world application to Indian agriculture or international conservation frameworks

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