UPHESC Assistant Professor Agricultural Botany PYQs

Concept: Modern (molecular/phylogenetic) classification of bacteria uses 16S rRNA gene sequencing, introduced by Carl Woese.

1. 16S rRNA is present in all prokaryotes, highly conserved with variable regions – ideal molecular clock.
2. Woese's 16S rRNA work gave the three-domain system (1990).
3. Gram staining, morphology and biochemical tests are classical, phenotypic methods.

Short trick: Woese + 16S = modern, molecular, three domains.

Concept: A basidium occurs only in Basidiomycotina; the forked 'tuning-fork' basidium is characteristic of jelly fungi (Dacrymycetales, e.g. Dacrymyces).

1. Holobasidium (club-shaped) – Agaricales; phragmobasidium (septate) – rusts, Tremella; tuning-fork – Dacrymyces.
2. Ascomycotina bear asci, Deuteromycotina have no sexual stage, Myxomycotina are slime moulds.

Short trick: No basidium outside Basidiomycotina – whatever its shape.

Concept: Flagellar arrangement: monotrichous (one polar flagellum), amphitrichous (one at each pole), lophotrichous (a tuft at one or both poles), peritrichous (all over the cell).

1. Thiobacillus – single polar flagellum → monotrichous (a-3). Nitrosomonas – polar flagella.
2. Salmonella and E. coli are both peritrichous, so List II has two peritrichous bacteria and nothing that is truly lophotrichous — no one-to-one match can be fully right.
3. Code (B) a-3, b-4, c-1, d-2 comes closest, but it calls Salmonella lophotrichous, which is wrong; (A) and (D) make E. coli or Salmonella monotrichous and (C) makes E. coli amphitrichous — also wrong.
4. As printed, no code is fully correct.

Short trick: Enteric rods (E. coli, Salmonella, Proteus) = peritrichous; Vibrio/Thiobacillus = monotrichous; Spirillum = lophotrichous.

Concept: R. H. Whittaker (1969) proposed five kingdoms: Monera, Protista, Fungi, Plantae, Animalia.

1. Criteria: cell type, body organisation, mode of nutrition, reproduction and phylogeny.
2. Tatum – one gene–one enzyme; Ehrlich – chemotherapy; Stanley – crystallised TMV.

Short trick: Whittaker 1969 – 5; Woese 1990 – 3 domains.

Concept: Antonie van Leeuwenhoek first saw and described bacteria and protozoa ('animalcules', 1676) with his own single-lens microscopes – Father of Microbiology.

1. Anton de Bary – Father of Mycology/modern plant pathology.
2. Winogradsky – Father of soil microbiology.
3. Stanley – crystallised TMV (Nobel 1946).

Short trick: Leeuwenhoek – first to see microbes.

Concept: Doi, Teranaka, Yora and Asuyama (1967, Japan) saw mycoplasma-like organisms in phloem of plants with yellows diseases (mulberry dwarf).

1. MLOs were renamed phytoplasmas in 1994.
2. Bawden & Pirie – TMV is a nucleoprotein; E. F. Smith – bacterial plant diseases.

Short trick: Doi 1967 – Japan – MLO.

Concept: Osmophiles (e.g. sugar-tolerant yeasts like Zygosaccharomyces) prefer media with high osmotic concentration, such as high sugar.

1. Halophiles need high salt; xerophiles tolerate low water activity/matric potential.
2. Most other microbes are inhibited by high osmotic pressure – the basis of preservation by sugar and salt.

Short trick: Osmo-phile = loves osmotic pressure (honey, jam).

Concept: Match each disease with its fungus.

1. Root rot – Rhizoctonia spp. (a-2).
2. Wheat rust – Puccinia (b-3).
3. Common smut of maize – Ustilago maydis (c-1).
4. Rice blast – Pyricularia oryzae (= Magnaporthe oryzae) (d-4).

Short trick: Smut = Ustilago, Rust = Puccinia, Blast = Pyricularia, Root rot = Rhizoctonia.

Concept: Phytoalexins are low-molecular-weight antimicrobial secondary metabolites synthesised de novo by plants after infection or stress (Müller & Börger, 1940).

1. Examples: pisatin (pea), phaseollin (bean), rishitin (potato), camalexin (Arabidopsis), glyceollin (soybean).
2. They are not hormones, not synthetic, and not lectins (proteins).

Short trick: Phyto-alexin = plant 'warding-off' compound made after attack.

Concept: Both statements are reported facts.

1. Indian workers (NABI, Mohali; Kaur et al. 2018) edited banana cv. Rasthali with CRISPR/Cas9, knocking out the PDS gene – albino plants served as a visible marker.
2. About 20 viruses (e.g. BBTV, BSV, BBrMV, CMV) are known to infect banana worldwide; CRISPR has also been used to inactivate endogenous banana streak virus sequences.

Short trick: PDS knockout = albino = proof that CRISPR worked.

Concept: Match each group with its hallmark.

1. Myxobacteria – gliding cells aggregate into multicellular fruiting bodies (a-1).
2. Methylotrophs – use reduced one-carbon compounds (formamide, cyanide, CO, methanol) (b-4).
3. Bacillus subtilis – forms endospores (c-2).
4. Mycoplasma – no cell wall, so penicillin-resistant; mostly parasitic (d-3).

Short trick: No wall → penicillin can't act → Mycoplasma.

Concept: A complete, infectious virus particle (nucleic acid + protein coat) is a virion.

1. Capsid – only the protein coat; nucleocapsid = capsid + nucleic acid.
2. Viroid – naked circular RNA without any protein coat (e.g. PSTVd).

Short trick: Virion = whole virus; capsid = coat only; viroid = RNA only.

Concept: Thiram is a dithiocarbamate – an organic sulphur fungicide (seed dressing).

1. Other dithiocarbamates: ziram, zineb, maneb, mancozeb.
2. Elemental sulphur – inorganic sulphur fungicide.
3. Bordeaux mixture and copper oxychloride – inorganic copper fungicides.

Short trick: Thi-ram, zi-ram, man-cozeb: carbamates = organic S.

Concept: Hyperplasia = overgrowth due to increased cell number (cell division), e.g. crown gall, club root.

1. Hypertrophy = overgrowth due to increased cell size.
2. Necrosis = death of cells/tissue.
3. Damping-off = seedling collapse (Pythium).

Short trick: Plasia = more cells; trophy = bigger cells.

Concept: All genes located on one chromosome form a linkage group; number of linkage groups = haploid chromosome number (n).

1. Linkage – the tendency (phenomenon) of genes to be inherited together.
2. Linkage map – the diagram showing their order and distances (cM).

Short trick: Group = set of genes; linkage = phenomenon; map = diagram.

Concept: An amphidiploid is an allopolyploid with the diploid complement of two or more different genomes; an allotetraploid has exactly two distinct genomes, each doubled (AABB).

1. Amphidiploid – two copies each of two or more genomes (a-2), e.g. hexaploid wheat AABBDD.
2. Allotetraploid – two copies each of two distinct genomes (b-3), e.g. Brassica juncea AABB.
3. Amphoteric – substance of dual (acid + base) nature (c-1).

Short trick: Tetra = exactly two genomes; amphi = two or more.

Concept: Hydroxylamine (NH₂OH) hydroxylates cytosine, which then pairs with A – it produces only GC → AT transitions, never AT → GC.

1. Mustard gas, EMS – alkylating agents.
2. Acridine orange, proflavin – intercalate, causing frameshifts.
3. Nitrous acid – deaminates A, C, G.

Short trick: Hydroxylamine is one-way: GC → AT only.

Concept: W. Johannsen (1903) proposed the pure-line theory working with the Princess variety of French bean (Phaseolus vulgaris) seed weight.

1. Selection is effective only among pure lines, not within a pure line (variation within is environmental).
2. Bulk method – Nilsson-Ehle (1908); backcross – Harlan & Pope (1922); progeny test – Vilmorin.

Short trick: Johannsen – beans – pure line – also coined 'gene', 'genotype', 'phenotype'.

Concept: Norin 10 is a Japanese semi-dwarf wheat carrying Rht1 and Rht2 (Rht-B1b, Rht-D1b) genes.

1. O. Vogel crossed it to produce Gaines; N. E. Borlaug used it to develop Mexican semi-dwarf wheats (Sonora 64, Lerma Rojo 64).
2. Rice dwarfing gene = sd1 from Dee-geo-woo-gen.

Short trick: Norin 10 → wheat; Dee-geo-woo-gen → rice.

Concept: The Golgi apparatus modifies (glycosylates), sorts and packages secretory materials into vesicles.

1. In plants it also synthesises non-cellulosic polysaccharides for the cell plate/wall.
2. Hydrolytic enzymes are held by lysosomes; membrane proteins are made on RER ribosomes.

Short trick: Golgi = cell's post office: pack and dispatch.