Match List – I with List – II and select the correct answer from the code given below the lists.
List – I (Plant disease)
A. Citrus Cracker
B. Red rot disease of sugar cane
C. Krishnakant disease of p

Question

Match List – I with List – II and select the correct answer from the code given below the lists.
List – I (Plant disease)
A. Citrus Cracker
B. Red rot disease of sugar cane
C. Krishnakant disease of potato
D. Sahu disease of wheat
List – II (Factor)
1. Insect
2. Deficiency of oxygen
3. Bacteria
4. Fungus
Code :

UnlockIAS · Accepted Answer

Correct — D, A-3, B-4, C-2, D-1. Take the three unambiguous rows first and the fourth follows. A, 'citrus cracker' — the paper's rendering of citrus canker — is bacterial: Xanthomonas citri, a rod-shaped Gram-negative bacterium with polar flagella, which leaves raised corky lesions on fruit, leaves and twigs; so A goes with 3. B, red rot of sugarcane, is the classic fungal disease of the crop, caused by Colletotrichum falcatum (teleomorph Glomerella tucumanensis); it is recorded in some 69 countries and has destroyed one commercial cane variety after another, so B goes with 4. C, the 'Krishnakant' condition of potato, is black heart — not an infection at all but a physiological disorder in which the inside of the tuber darkens and dies because oxygen cannot reach it, in waterlogged soil or in badly ventilated storage; so C goes with 2, deficiency of oxygen. That leaves only 1, insect, for D, the 'Sahu' or 'Sehu' disease of wheat — the ear-cockle and tundu complex. One caution on that last pairing is given below and in the concept note: the actual agent of ear cockle is a nematode, not an insect. The mapping A-3, B-4, C-2, D-1 is option (d).

Why the other options are wrong — (a) It misplaces all four. Citrus canker is bacterial rather than an insect problem; red rot is fungal, not bacterial; the potato disorder is a matter of oxygen supply, not a fungus; and wheat's ear-cockle disease is not caused by a lack of oxygen. The single easiest check is red rot — a textbook fungal disease of sugarcane — and this option gets it wrong.  (b) This is the 'straight run' option, matching A to 1, B to 2, C to 3 and D to 4 in order — a pattern worth distrusting on sight. Every pair fails: it makes red rot an oxygen-deficiency disorder and the potato condition bacterial, when it is exactly the reverse.  (c) It swaps the two microbial agents onto the wrong hosts, calling citrus canker fungal and the potato disorder bacterial, and it makes red rot of sugarcane an insect problem. Red rot is caused by Colletotrichum falcatum, a fungus; the borers and the pyrilla are the insect pests of cane, and they are a separate story.

Concept: Plant diseases are classified first by the kind of agent behind them, and the four possibilities in List-II cover three of the main classes. Bacteria (citrus canker) and fungi (red rot) are parasitic pathogens, spread from plant to plant. Animal pests — insects, mites and nematodes — are a third class, which damage tissue directly or carry pathogens with them. The fourth entry, oxygen deficiency, belongs to an entirely different family: physiological or non-parasitic disorders, produced by the environment rather than by any organism, and therefore not contagious. Potato black heart is the classic example — waterlogged soil or an unventilated store starves the tuber's interior of oxygen, its cells suffocate, and the flesh blackens from the middle outward.

State PCS 2022 Q34 — Science & Technology PYQ with Answer

State PCS 2022 Q34 — Science & Technology PYQ with Answer