(a) Discuss about the names of causal organisms, symptoms, disease cycle and management of loose smut of wheat. What are the differences between rust and smut fungi? (20 marks)
(b) Enumerate the salient features of fossil gymnosperms using suitable e

Question

(a) Discuss about the names of causal organisms, symptoms, disease cycle and management of loose smut of wheat. What are the differences between rust and smut fungi? (20 marks)
(b) Enumerate the salient features of fossil gymnosperms using suitable examples with special reference to Bennettitales and Cordaitales. (20 marks)
(c) Give the general characteristics of bryophytes. Enlist the resemblances and differences of bryophytes with pteridophytes. (10 marks)

UPSC Answer Check · Accepted Answer

Begin with a brief introduction acknowledging the diversity of plant groups covered. For part (a), spend approximately 40% of your effort (8 marks worth) discussing Ustilago tritici, its disease cycle with emphasis on systemic infection, and clearly differentiate rust (Puccinia, heteroecious, complex life cycle) from smut (Ustilago, autoecious, simple life cycle) fungi. For part (b), allocate 40% (8 marks worth) enumerating fossil gymnosperm characteristics with detailed treatment of Bennettitales (Cycadeoidea, flower-like strobili) and Cordaitales (Cordaites, secondary wood). For part (c), use remaining 20% (4 marks worth) for bryophyte characteristics and systematic comparison with pteridophytes. Conclude by synthesizing evolutionary trends across these plant groups.
- Part (a): Causal organism Ustilago tritici (syn. U. nuda f.sp. tritici); symptoms include black powdery sori replacing grains; disease cycle showing seed-borne inoculum, systemic infection, teliospore germination and management through hot water treatment, resistant varieties like HD-2967 and systemic fungicides
- Part (a): Clear distinction between rust fungi (Puccinia spp., obligate parasites, heteroecious, macrocyclic with 5 spore stages, orange-brown pustules) and smut fungi (Ustilago spp., facultative parasites, autoecious, simple life cycle, dark sooty spore masses)
- Part (b): General features of fossil gymnosperms - dominance in Carboniferous-Permian, heterospory, seed habit origin, secondary growth; Bennettitales (Cycadeoidea, Williamsonia) with bisexual flower-like strobili, synangia, absence of true flowers
- Part (b): Cordaitales (Cordaites, Mesoxylon) with tall trees, pycnoxylic wood, simple leaves, terminal strobili, platyspermic seeds; significance in coal formation (Gondwana deposits of India)
- Part (c): Bryophyte characteristics - amphibious, dominant gametophyte, dependent sporophyte, rhizoids, absence of vascular tissue, heteromorphic alternation of generations
- Part (c): Resemblances with pteridophytes (chlorophyllous, autotrophic, heteromorphic alternation, jacketed antheridia, archegonia with neck canal cells) and differences (vascular tissue presence, independent sporophyte, true roots, leaves, stomata in pteridophytes)
- Evolutionary significance: Progression from bryophytes to pteridophytes showing land plant adaptation; fossil gymnosperms as evolutionary bridge between pteridophytes and angiosperms
- Indian relevance: Mention of Gondwana fossil records (Damuda series), wheat cultivation zones in Indo-Gangetic plains affected by loose smut

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Accurately identifies Ustilago tritici as loose smut pathogen with correct disease cycle (seed-borne, systemic infection); precisely describes Bennettitales flower-like structures and Cordaitales wood anatomy; correctly distinguishes bryophyte gametophyte dominance from pteridophyte sporophyte dominance with accurate evolutionary relationships	Identifies causal organism correctly but confuses systemic vs local infection; describes fossil gymnosperms generally but mixes Bennettitales with Cycadales; lists bryophyte-pteridophyte differences with minor errors in alternation of generations	Wrongly identifies causal organism (confuses with covered smut/bunt); fundamental confusion between rust and smut life cycles; misidentifies fossil characteristics or treats Bennettitales as angiosperms; incorrect understanding of dominant generation in bryophytes
Diagram / labelling	15%	7.5	Includes well-labelled diagram of Ustilago disease cycle showing teliospore, basidiospore, infection pathway; sketches Bennettitales strobilus (Cycadeoidea) and Cordaites leaf/wood structure; draws bryophyte life cycle (Funaria/Marchantia) with clear sporophyte-gametophyte relationship	Provides basic disease cycle diagram with some labels; rough sketch of fossil plant habit without anatomical details; simple bryophyte diagram showing thallus and sporophyte but missing key structures like archegonium or antheridium	No diagrams or poorly drawn unlabelled sketches; diagrams with major structural errors; diagrams copied without understanding relevance to question parts
Examples & nomenclature	20%	10	Cites specific examples: Ustilago tritici (perfect name), resistant Indian wheat varieties (HD-2967, PBW-343); Williamsonia sewardiana, Cycadeoidea from Bennettitales; Cordaites, Mesoxylon from Cordaitales; Funaria, Marchantia for bryophytes and Selaginella, Pteris for pteridophyte comparison; mentions Gondwana fossil sites	Gives generic examples (Ustilago without species, 'cycadeoid' without genus); mentions Cordaitales without specific genera; common bryophytes named but no specific pteridophytes for comparison; no Indian context	Wrong examples (Puccinia for smut, living cycads for Bennettitales); no examples for fossil gymnosperms; confuses bryophyte and pteridophyte examples; invented or irrelevant examples
Process explanation	25%	12.5	Explains loose smut disease cycle stepwise: teliospore survival on seed, germination with host, systemic mycelium, sorus formation; clearly contrasts rust (heteroecious, 5 spore types) and smut (autoecious, 2-3 spore types) life cycles; details Bennettitales reproduction with synangia and pollen chambers; systematic comparison table for bryophyte-pteridophyte characteristics	Describes disease cycle generally without clear infection stages; lists differences between rust and smut without explaining life cycle complexity; describes fossil features as static characteristics rather than processes; comparison of plant groups as bullet points without systematic organization	Confused or circular explanation of disease cycle; no clear distinction between rust and smut life cycles; describes fossils as 'primitive plants' without specific processes; random listing of characteristics without logical comparison structure
Application / ecology	15%	7.5	Discusses management: hot water treatment (52°C, 10-12 min), systemic fungicides (Carbendazim), resistant varieties for Indian agro-climatic zones; ecological significance of Cordaitales in Carboniferous coal formation (Damuda series of India); evolutionary importance of heterospory leading to seed habit; conservation relevance of bryophytes as pioneer species	Mentions chemical control without specifics; notes fossil gymnosperms as 'ancient' without ecological context; brief mention of bryophytes in succession without ecological role; generic management suggestions without Indian relevance	No management strategies for loose smut; no ecological or evolutionary significance discussed; irrelevant applications (medicinal uses not asked); completely misses agricultural importance of wheat disease control in Indian context

Q3

Directive word: Discuss

How this answer will be evaluated

Approach

Key points expected

Evaluation rubric

Practice this exact question

More from Botany 2021 Paper I